diff --git a/hal/include/HAL/cpp/Log.h b/hal/include/HAL/cpp/Log.h
index 4ddbd4fe24..528cda3891 100644
--- a/hal/include/HAL/cpp/Log.h
+++ b/hal/include/HAL/cpp/Log.h
@@ -10,9 +10,11 @@
 #include <chrono>
 #include <iomanip>
 #include <iostream>
-#include <sstream>
 #include <string>
 
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
+
 inline std::string NowTime();
 
 enum TLogLevel {
@@ -31,7 +33,7 @@ class Log {
  public:
   Log();
   virtual ~Log();
-  std::ostringstream& Get(TLogLevel level = logINFO);
+  llvm::raw_ostream& Get(TLogLevel level = logINFO);
 
  public:
   static TLogLevel& ReportingLevel();
@@ -39,7 +41,8 @@ class Log {
   static TLogLevel FromString(const std::string& level);
 
  protected:
-  std::ostringstream os;
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream oss{buf};
 
  private:
   Log(const Log&);
@@ -48,16 +51,16 @@ class Log {
 
 inline Log::Log() {}
 
-inline std::ostringstream& Log::Get(TLogLevel level) {
-  os << "- " << NowTime();
-  os << " " << ToString(level) << ": ";
-  os << std::string(level > logDEBUG ? level - logDEBUG : 0, '\t');
-  return os;
+inline llvm::raw_ostream& Log::Get(TLogLevel level) {
+  oss << "- " << NowTime();
+  oss << " " << ToString(level) << ": ";
+  oss << std::string(level > logDEBUG ? level - logDEBUG : 0, '\t');
+  return oss;
 }
 
 inline Log::~Log() {
-  os << std::endl;
-  std::cerr << os.str();
+  oss << "\n";
+  std::cerr << oss.str();
 }
 
 inline TLogLevel& Log::ReportingLevel() {
@@ -96,16 +99,29 @@ typedef Log FILELog;
   Log().Get(level)
 
 inline std::string NowTime() {
-  std::stringstream ss;
-  ss << std::setfill('0') << std::setw(2);
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream oss(buf);
 
   using namespace std::chrono;
   auto now = system_clock::now().time_since_epoch();
 
-  ss << duration_cast<hours>(now).count() % 24 << ":"
-     << duration_cast<minutes>(now).count() % 60 << ":"
-     << duration_cast<seconds>(now).count() % 60 << "."
-     << duration_cast<milliseconds>(now).count() % 1000;
+  // Hours
+  auto count = duration_cast<hours>(now).count() % 24;
+  if (count < 10) oss << "0";
+  oss << count << ":";
 
-  return ss.str();
+  // Minutes
+  count = duration_cast<minutes>(now).count() % 60;
+  if (count < 10) oss << "0";
+  oss << count << ":";
+
+  // Seconds
+  count = duration_cast<seconds>(now).count() % 60;
+  if (count < 10) oss << "0";
+  oss << count << ".";
+
+  // Milliseconds
+  oss << duration_cast<milliseconds>(now).count() % 1000;
+
+  return oss.str();
 }
diff --git a/wpilibc/athena/include/MotorSafety.h b/wpilibc/athena/include/MotorSafety.h
index 27c938cd9d..d78c310209 100644
--- a/wpilibc/athena/include/MotorSafety.h
+++ b/wpilibc/athena/include/MotorSafety.h
@@ -9,7 +9,7 @@
 
 #define DEFAULT_SAFETY_EXPIRATION 0.1
 
-#include <sstream>
+#include "llvm/raw_ostream.h"
 
 namespace frc {
 
@@ -21,7 +21,7 @@ class MotorSafety {
   virtual void StopMotor() = 0;
   virtual void SetSafetyEnabled(bool enabled) = 0;
   virtual bool IsSafetyEnabled() const = 0;
-  virtual void GetDescription(std::ostringstream& desc) const = 0;
+  virtual void GetDescription(llvm::raw_ostream& desc) const = 0;
 };
 
 }  // namespace frc
diff --git a/wpilibc/athena/include/Relay.h b/wpilibc/athena/include/Relay.h
index eac39673f8..019c61cc27 100644
--- a/wpilibc/athena/include/Relay.h
+++ b/wpilibc/athena/include/Relay.h
@@ -14,6 +14,7 @@
 #include "LiveWindow/LiveWindowSendable.h"
 #include "MotorSafety.h"
 #include "SensorBase.h"
+#include "llvm/raw_ostream.h"
 #include "tables/ITable.h"
 #include "tables/ITableListener.h"
 
@@ -53,7 +54,7 @@ class Relay : public MotorSafety,
   void StopMotor() override;
   bool IsSafetyEnabled() const override;
   void SetSafetyEnabled(bool enabled) override;
-  void GetDescription(std::ostringstream& desc) const override;
+  void GetDescription(llvm::raw_ostream& desc) const override;
 
   void ValueChanged(ITable* source, llvm::StringRef key,
                     std::shared_ptr<nt::Value> value, bool isNew) override;
diff --git a/wpilibc/athena/include/RobotDrive.h b/wpilibc/athena/include/RobotDrive.h
index 219ef9e1e2..0c5fddab0a 100644
--- a/wpilibc/athena/include/RobotDrive.h
+++ b/wpilibc/athena/include/RobotDrive.h
@@ -8,11 +8,11 @@
 #pragma once
 
 #include <memory>
-#include <sstream>
 
 #include "ErrorBase.h"
 #include "MotorSafety.h"
 #include "MotorSafetyHelper.h"
+#include "llvm/raw_ostream.h"
 
 namespace frc {
 
@@ -94,7 +94,7 @@ class RobotDrive : public MotorSafety, public ErrorBase {
   void StopMotor() override;
   bool IsSafetyEnabled() const override;
   void SetSafetyEnabled(bool enabled) override;
-  void GetDescription(std::ostringstream& desc) const override;
+  void GetDescription(llvm::raw_ostream& desc) const override;
 
  protected:
   void InitRobotDrive();
diff --git a/wpilibc/athena/include/SafePWM.h b/wpilibc/athena/include/SafePWM.h
index 16a64c1045..b9c92af6d3 100644
--- a/wpilibc/athena/include/SafePWM.h
+++ b/wpilibc/athena/include/SafePWM.h
@@ -8,11 +8,11 @@
 #pragma once
 
 #include <memory>
-#include <sstream>
 
 #include "MotorSafety.h"
 #include "MotorSafetyHelper.h"
 #include "PWM.h"
+#include "llvm/raw_ostream.h"
 
 namespace frc {
 
@@ -34,7 +34,7 @@ class SafePWM : public PWM, public MotorSafety {
   void StopMotor();
   bool IsSafetyEnabled() const;
   void SetSafetyEnabled(bool enabled);
-  void GetDescription(std::ostringstream& desc) const;
+  void GetDescription(llvm::raw_ostream& desc) const;
 
   virtual void SetSpeed(double speed);
 
diff --git a/wpilibc/athena/src/AnalogInput.cpp b/wpilibc/athena/src/AnalogInput.cpp
index d370c3a7f1..2e59eaa01c 100644
--- a/wpilibc/athena/src/AnalogInput.cpp
+++ b/wpilibc/athena/src/AnalogInput.cpp
@@ -8,14 +8,14 @@
 #include "AnalogInput.h"
 #include "HAL/AnalogInput.h"
 
-#include <sstream>
-
 #include "HAL/AnalogAccumulator.h"
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "LiveWindow/LiveWindow.h"
 #include "Timer.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -30,7 +30,8 @@ const int AnalogInput::kAccumulatorChannels[] = {0, 1};
  *                on-board 4-7 are on the MXP port.
  */
 AnalogInput::AnalogInput(int channel) {
-  std::stringstream buf;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
   buf << "Analog Input " << channel;
 
   if (!SensorBase::CheckAnalogInputChannel(channel)) {
diff --git a/wpilibc/athena/src/AnalogOutput.cpp b/wpilibc/athena/src/AnalogOutput.cpp
index 3905ae12aa..7cbf9e2c97 100644
--- a/wpilibc/athena/src/AnalogOutput.cpp
+++ b/wpilibc/athena/src/AnalogOutput.cpp
@@ -8,12 +8,13 @@
 #include "AnalogOutput.h"
 
 #include <limits>
-#include <sstream>
 
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -25,8 +26,9 @@ using namespace frc;
  * @param channel The channel number on the roboRIO to represent.
  */
 AnalogOutput::AnalogOutput(int channel) {
-  std::stringstream buf;
-  buf << "analog input " << channel;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
+  buf << "analog output " << channel;
 
   if (!SensorBase::CheckAnalogOutputChannel(channel)) {
     wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, buf.str());
diff --git a/wpilibc/athena/src/DigitalInput.cpp b/wpilibc/athena/src/DigitalInput.cpp
index 2eeefbb7f4..13447c8838 100644
--- a/wpilibc/athena/src/DigitalInput.cpp
+++ b/wpilibc/athena/src/DigitalInput.cpp
@@ -8,13 +8,14 @@
 #include "DigitalInput.h"
 
 #include <limits>
-#include <sstream>
 
 #include "HAL/DIO.h"
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -26,7 +27,8 @@ using namespace frc;
  * @param channel The DIO channel 0-9 are on-board, 10-25 are on the MXP port
  */
 DigitalInput::DigitalInput(int channel) {
-  std::stringstream buf;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
 
   if (!CheckDigitalChannel(channel)) {
     buf << "Digital Channel " << channel;
diff --git a/wpilibc/athena/src/DigitalOutput.cpp b/wpilibc/athena/src/DigitalOutput.cpp
index 381df60c7f..a9e3942fec 100644
--- a/wpilibc/athena/src/DigitalOutput.cpp
+++ b/wpilibc/athena/src/DigitalOutput.cpp
@@ -8,12 +8,13 @@
 #include "DigitalOutput.h"
 
 #include <limits>
-#include <sstream>
 
 #include "HAL/DIO.h"
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -26,7 +27,8 @@ using namespace frc;
  *                port
  */
 DigitalOutput::DigitalOutput(int channel) {
-  std::stringstream buf;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
 
   m_pwmGenerator = HAL_kInvalidHandle;
   if (!CheckDigitalChannel(channel)) {
diff --git a/wpilibc/athena/src/DoubleSolenoid.cpp b/wpilibc/athena/src/DoubleSolenoid.cpp
index 1954adaf68..a2f92d4274 100644
--- a/wpilibc/athena/src/DoubleSolenoid.cpp
+++ b/wpilibc/athena/src/DoubleSolenoid.cpp
@@ -7,13 +7,13 @@
 
 #include "DoubleSolenoid.h"
 
-#include <sstream>
-
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "HAL/Solenoid.h"
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -41,7 +41,8 @@ DoubleSolenoid::DoubleSolenoid(int moduleNumber, int forwardChannel,
     : SolenoidBase(moduleNumber),
       m_forwardChannel(forwardChannel),
       m_reverseChannel(reverseChannel) {
-  std::stringstream buf;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
   if (!CheckSolenoidModule(m_moduleNumber)) {
     buf << "Solenoid Module " << m_moduleNumber;
     wpi_setWPIErrorWithContext(ModuleIndexOutOfRange, buf.str());
diff --git a/wpilibc/athena/src/MotorSafetyHelper.cpp b/wpilibc/athena/src/MotorSafetyHelper.cpp
index c42be31695..31f13ffd6e 100644
--- a/wpilibc/athena/src/MotorSafetyHelper.cpp
+++ b/wpilibc/athena/src/MotorSafetyHelper.cpp
@@ -7,12 +7,12 @@
 
 #include "MotorSafetyHelper.h"
 
-#include <sstream>
-
 #include "DriverStation.h"
 #include "MotorSafety.h"
 #include "Timer.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -95,10 +95,11 @@ void MotorSafetyHelper::Check() {
 
   std::lock_guard<hal::priority_recursive_mutex> sync(m_syncMutex);
   if (m_stopTime < Timer::GetFPGATimestamp()) {
-    std::ostringstream desc;
+    llvm::SmallString<128> buf;
+    llvm::raw_svector_ostream desc(buf);
     m_safeObject->GetDescription(desc);
     desc << "... Output not updated often enough.";
-    wpi_setWPIErrorWithContext(Timeout, desc.str().c_str());
+    wpi_setWPIErrorWithContext(Timeout, desc.str());
     m_safeObject->StopMotor();
   }
 }
diff --git a/wpilibc/athena/src/PWM.cpp b/wpilibc/athena/src/PWM.cpp
index 4883e16e1f..85d16d01c1 100644
--- a/wpilibc/athena/src/PWM.cpp
+++ b/wpilibc/athena/src/PWM.cpp
@@ -8,12 +8,12 @@
 #include "HAL/PWM.h"
 #include "PWM.h"
 
-#include <sstream>
-
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "Utility.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -28,7 +28,8 @@ using namespace frc;
  *                MXP port
  */
 PWM::PWM(int channel) {
-  std::stringstream buf;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
 
   if (!CheckPWMChannel(channel)) {
     buf << "PWM Channel " << channel;
diff --git a/wpilibc/athena/src/PowerDistributionPanel.cpp b/wpilibc/athena/src/PowerDistributionPanel.cpp
index 6fc33dfc67..8f778b9b51 100644
--- a/wpilibc/athena/src/PowerDistributionPanel.cpp
+++ b/wpilibc/athena/src/PowerDistributionPanel.cpp
@@ -7,13 +7,13 @@
 
 #include "PowerDistributionPanel.h"
 
-#include <sstream>
-
 #include "HAL/HAL.h"
 #include "HAL/PDP.h"
 #include "HAL/Ports.h"
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -76,7 +76,8 @@ double PowerDistributionPanel::GetCurrent(int channel) const {
   int32_t status = 0;
 
   if (!CheckPDPChannel(channel)) {
-    std::stringstream buf;
+    llvm::SmallString<32> str;
+    llvm::raw_svector_ostream buf(str);
     buf << "PDP Channel " << channel;
     wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, buf.str());
   }
diff --git a/wpilibc/athena/src/Relay.cpp b/wpilibc/athena/src/Relay.cpp
index 8e3a7b0f5e..78e0d9372a 100644
--- a/wpilibc/athena/src/Relay.cpp
+++ b/wpilibc/athena/src/Relay.cpp
@@ -8,13 +8,12 @@
 #include "HAL/Relay.h"
 #include "Relay.h"
 
-#include <sstream>
-
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "LiveWindow/LiveWindow.h"
 #include "MotorSafetyHelper.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
 
 using namespace frc;
 
@@ -29,7 +28,8 @@ using namespace frc;
  */
 Relay::Relay(int channel, Relay::Direction direction)
     : m_channel(channel), m_direction(direction) {
-  std::stringstream buf;
+  llvm::SmallString<128> str;
+  llvm::raw_svector_ostream buf(str);
   if (!SensorBase::CheckRelayChannel(m_channel)) {
     buf << "Relay Channel " << m_channel;
     wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, buf.str());
@@ -268,7 +268,7 @@ bool Relay::IsSafetyEnabled() const {
   return m_safetyHelper->IsSafetyEnabled();
 }
 
-void Relay::GetDescription(std::ostringstream& desc) const {
+void Relay::GetDescription(llvm::raw_ostream& desc) const {
   desc << "Relay " << GetChannel();
 }
 
diff --git a/wpilibc/athena/src/RobotDrive.cpp b/wpilibc/athena/src/RobotDrive.cpp
index e5c06d1238..25143efc6c 100644
--- a/wpilibc/athena/src/RobotDrive.cpp
+++ b/wpilibc/athena/src/RobotDrive.cpp
@@ -718,7 +718,7 @@ void RobotDrive::SetSafetyEnabled(bool enabled) {
   m_safetyHelper->SetSafetyEnabled(enabled);
 }
 
-void RobotDrive::GetDescription(std::ostringstream& desc) const {
+void RobotDrive::GetDescription(llvm::raw_ostream& desc) const {
   desc << "RobotDrive";
 }
 
diff --git a/wpilibc/athena/src/SafePWM.cpp b/wpilibc/athena/src/SafePWM.cpp
index cd62192852..e98833f88f 100644
--- a/wpilibc/athena/src/SafePWM.cpp
+++ b/wpilibc/athena/src/SafePWM.cpp
@@ -74,7 +74,7 @@ bool SafePWM::IsSafetyEnabled() const {
   return m_safetyHelper->IsSafetyEnabled();
 }
 
-void SafePWM::GetDescription(std::ostringstream& desc) const {
+void SafePWM::GetDescription(llvm::raw_ostream& desc) const {
   desc << "PWM " << GetChannel();
 }
 
diff --git a/wpilibc/athena/src/Solenoid.cpp b/wpilibc/athena/src/Solenoid.cpp
index d70c3c36d7..9dfdc333a0 100644
--- a/wpilibc/athena/src/Solenoid.cpp
+++ b/wpilibc/athena/src/Solenoid.cpp
@@ -8,12 +8,12 @@
 #include "HAL/Solenoid.h"
 #include "Solenoid.h"
 
-#include <sstream>
-
 #include "HAL/HAL.h"
 #include "HAL/Ports.h"
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -33,7 +33,8 @@ Solenoid::Solenoid(int channel)
  */
 Solenoid::Solenoid(int moduleNumber, int channel)
     : SolenoidBase(moduleNumber), m_channel(channel) {
-  std::stringstream buf;
+  llvm::SmallString<32> str;
+  llvm::raw_svector_ostream buf(str);
   if (!CheckSolenoidModule(m_moduleNumber)) {
     buf << "Solenoid Module " << m_moduleNumber;
     wpi_setWPIErrorWithContext(ModuleIndexOutOfRange, buf.str());
diff --git a/wpilibc/athena/src/Utility.cpp b/wpilibc/athena/src/Utility.cpp
index 1a5325167d..cbf2c99b6a 100644
--- a/wpilibc/athena/src/Utility.cpp
+++ b/wpilibc/athena/src/Utility.cpp
@@ -13,12 +13,12 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
-#include <sstream>
 
 #include "ErrorBase.h"
 #include "HAL/DriverStation.h"
 #include "HAL/HAL.h"
 #include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -32,19 +32,21 @@ bool wpi_assert_impl(bool conditionValue, llvm::StringRef conditionText,
                      llvm::StringRef message, llvm::StringRef fileName,
                      int lineNumber, llvm::StringRef funcName) {
   if (!conditionValue) {
-    std::stringstream locStream;
+    llvm::SmallString<128> locBuf;
+    llvm::raw_svector_ostream locStream(locBuf);
     locStream << funcName << " [";
     llvm::SmallString<128> fileTemp;
     locStream << basename(fileName.c_str(fileTemp)) << ":" << lineNumber << "]";
 
-    std::stringstream errorStream;
+    llvm::SmallString<128> errorBuf;
+    llvm::raw_svector_ostream errorStream(errorBuf);
 
     errorStream << "Assertion \"" << conditionText << "\" ";
 
     if (!message.empty()) {
-      errorStream << "failed: " << message << std::endl;
+      errorStream << "failed: " << message << "\n";
     } else {
-      errorStream << "failed." << std::endl;
+      errorStream << "failed.\n";
     }
 
     std::string stack = GetStackTrace(2);
@@ -68,20 +70,22 @@ void wpi_assertEqual_common_impl(llvm::StringRef valueA, llvm::StringRef valueB,
                                  llvm::StringRef message,
                                  llvm::StringRef fileName, int lineNumber,
                                  llvm::StringRef funcName) {
-  std::stringstream locStream;
+  llvm::SmallString<128> locBuf;
+  llvm::raw_svector_ostream locStream(locBuf);
   locStream << funcName << " [";
   llvm::SmallString<128> fileTemp;
   locStream << basename(fileName.c_str(fileTemp)) << ":" << lineNumber << "]";
 
-  std::stringstream errorStream;
+  llvm::SmallString<128> errorBuf;
+  llvm::raw_svector_ostream errorStream(errorBuf);
 
   errorStream << "Assertion \"" << valueA << " " << equalityType << " "
               << valueB << "\" ";
 
   if (!message.empty()) {
-    errorStream << "failed: " << message << std::endl;
+    errorStream << "failed: " << message << "\n";
   } else {
-    errorStream << "failed." << std::endl;
+    errorStream << "failed.\n";
   }
 
   std::string trace = GetStackTrace(3);
@@ -217,12 +221,13 @@ std::string GetStackTrace(int offset) {
   void* stackTrace[128];
   int stackSize = backtrace(stackTrace, 128);
   char** mangledSymbols = backtrace_symbols(stackTrace, stackSize);
-  std::stringstream trace;
+  llvm::SmallString<1024> buf;
+  llvm::raw_svector_ostream trace(buf);
 
   for (int i = offset; i < stackSize; i++) {
     // Only print recursive functions once in a row.
     if (i == 0 || stackTrace[i] != stackTrace[i - 1]) {
-      trace << "\tat " << demangle(mangledSymbols[i]) << std::endl;
+      trace << "\tat " << demangle(mangledSymbols[i]) << "\n";
     }
   }
 
diff --git a/wpilibc/shared/src/Error.cpp b/wpilibc/shared/src/Error.cpp
index b853b5046c..3feed2702e 100644
--- a/wpilibc/shared/src/Error.cpp
+++ b/wpilibc/shared/src/Error.cpp
@@ -7,11 +7,11 @@
 
 #include "Error.h"
 
-#include <sstream>
-
 #include "DriverStation.h"
 #include "Timer.h"
 #include "Utility.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -64,7 +64,8 @@ void Error::Set(Code code, llvm::StringRef contextMessage,
 }
 
 void Error::Report() {
-  std::stringstream locStream;
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream locStream(buf);
   locStream << m_function << " [";
 
 #if defined(_WIN32)
diff --git a/wpilibc/shared/src/ErrorBase.cpp b/wpilibc/shared/src/ErrorBase.cpp
index 36141e4227..5cfcb04aef 100644
--- a/wpilibc/shared/src/ErrorBase.cpp
+++ b/wpilibc/shared/src/ErrorBase.cpp
@@ -15,6 +15,8 @@
 
 #define WPI_ERRORS_DEFINE_STRINGS
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -83,7 +85,8 @@ void ErrorBase::SetImaqError(int success, llvm::StringRef contextMessage,
                              int lineNumber) const {
   // If there was an error
   if (success <= 0) {
-    std::stringstream err;
+    llvm::SmallString<128> buf;
+    llvm::raw_svector_ostream err(buf);
     err << success << ": " << contextMessage;
 
     // Set the current error information for this object.
diff --git a/wpilibc/shared/src/LiveWindow/LiveWindow.cpp b/wpilibc/shared/src/LiveWindow/LiveWindow.cpp
index 1328545744..91c6523b94 100644
--- a/wpilibc/shared/src/LiveWindow/LiveWindow.cpp
+++ b/wpilibc/shared/src/LiveWindow/LiveWindow.cpp
@@ -8,8 +8,9 @@
 #include "LiveWindow/LiveWindow.h"
 
 #include <algorithm>
-#include <sstream>
 
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 #include "networktables/NetworkTable.h"
 
 using namespace frc;
@@ -154,7 +155,8 @@ void LiveWindow::AddActuator(const std::string& subsystem,
  */
 void LiveWindow::AddSensor(std::string type, int channel,
                            LiveWindowSendable* component) {
-  std::ostringstream oss;
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream oss(buf);
   oss << type << "[" << channel << "]";
   AddSensor("Ungrouped", oss.str(), component);
   std::shared_ptr<LiveWindowSendable> component_stl(
@@ -169,7 +171,8 @@ void LiveWindow::AddSensor(std::string type, int channel,
  */
 void LiveWindow::AddActuator(std::string type, int channel,
                              LiveWindowSendable* component) {
-  std::ostringstream oss;
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream oss(buf);
   oss << type << "[" << channel << "]";
   AddActuator("Ungrouped", oss.str(),
               std::shared_ptr<LiveWindowSendable>(component,
@@ -181,7 +184,8 @@ void LiveWindow::AddActuator(std::string type, int channel,
  */
 void LiveWindow::AddActuator(std::string type, int module, int channel,
                              LiveWindowSendable* component) {
-  std::ostringstream oss;
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream oss(buf);
   oss << type << "[" << module << "," << channel << "]";
   AddActuator("Ungrouped", oss.str(),
               std::shared_ptr<LiveWindowSendable>(component,
diff --git a/wpilibc/sim/include/MotorSafety.h b/wpilibc/sim/include/MotorSafety.h
index 27c938cd9d..d78c310209 100644
--- a/wpilibc/sim/include/MotorSafety.h
+++ b/wpilibc/sim/include/MotorSafety.h
@@ -9,7 +9,7 @@
 
 #define DEFAULT_SAFETY_EXPIRATION 0.1
 
-#include <sstream>
+#include "llvm/raw_ostream.h"
 
 namespace frc {
 
@@ -21,7 +21,7 @@ class MotorSafety {
   virtual void StopMotor() = 0;
   virtual void SetSafetyEnabled(bool enabled) = 0;
   virtual bool IsSafetyEnabled() const = 0;
-  virtual void GetDescription(std::ostringstream& desc) const = 0;
+  virtual void GetDescription(llvm::raw_ostream& desc) const = 0;
 };
 
 }  // namespace frc
diff --git a/wpilibc/sim/include/Relay.h b/wpilibc/sim/include/Relay.h
index 19ddd7d9a1..f8b640f848 100644
--- a/wpilibc/sim/include/Relay.h
+++ b/wpilibc/sim/include/Relay.h
@@ -13,6 +13,7 @@
 #include "LiveWindow/LiveWindowSendable.h"
 #include "MotorSafety.h"
 #include "SensorBase.h"
+#include "llvm/raw_ostream.h"
 #include "simulation/SimContinuousOutput.h"
 #include "tables/ITable.h"
 #include "tables/ITableListener.h"
@@ -55,7 +56,7 @@ class Relay : public MotorSafety,
   void StopMotor() override;
   bool IsSafetyEnabled() const override;
   void SetSafetyEnabled(bool enabled) override;
-  void GetDescription(std::ostringstream& desc) const override;
+  void GetDescription(llvm::raw_ostream& desc) const override;
 
   void ValueChanged(ITable* source, llvm::StringRef key,
                     std::shared_ptr<nt::Value> value, bool isNew) override;
diff --git a/wpilibc/sim/include/RobotDrive.h b/wpilibc/sim/include/RobotDrive.h
index de4306ad87..2f892d1870 100644
--- a/wpilibc/sim/include/RobotDrive.h
+++ b/wpilibc/sim/include/RobotDrive.h
@@ -14,6 +14,7 @@
 #include "ErrorBase.h"
 #include "MotorSafety.h"
 #include "MotorSafetyHelper.h"
+#include "llvm/raw_ostream.h"
 
 namespace frc {
 
@@ -97,7 +98,7 @@ class RobotDrive : public MotorSafety, public ErrorBase {
   void StopMotor() override;
   bool IsSafetyEnabled() const override;
   void SetSafetyEnabled(bool enabled) override;
-  void GetDescription(std::ostringstream& desc) const override;
+  void GetDescription(llvm::raw_ostream& desc) const override;
 
  protected:
   void InitRobotDrive();
diff --git a/wpilibc/sim/include/SafePWM.h b/wpilibc/sim/include/SafePWM.h
index 91eaa8e54c..108f688307 100644
--- a/wpilibc/sim/include/SafePWM.h
+++ b/wpilibc/sim/include/SafePWM.h
@@ -12,6 +12,7 @@
 #include "MotorSafety.h"
 #include "MotorSafetyHelper.h"
 #include "PWM.h"
+#include "llvm/raw_ostream.h"
 
 namespace frc {
 
@@ -34,7 +35,7 @@ class SafePWM : public PWM, public MotorSafety {
   void StopMotor();
   bool IsSafetyEnabled() const;
   void SetSafetyEnabled(bool enabled);
-  void GetDescription(std::ostringstream& desc) const;
+  void GetDescription(llvm::raw_ostream& desc) const;
 
   virtual void SetSpeed(double speed);
 
diff --git a/wpilibc/sim/src/AnalogGyro.cpp b/wpilibc/sim/src/AnalogGyro.cpp
index 77b231c652..1d697a84ae 100644
--- a/wpilibc/sim/src/AnalogGyro.cpp
+++ b/wpilibc/sim/src/AnalogGyro.cpp
@@ -7,11 +7,11 @@
 
 #include "AnalogGyro.h"
 
-#include <sstream>
-
 #include "LiveWindow/LiveWindow.h"
 #include "Timer.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -34,9 +34,10 @@ const double AnalogGyro::kDefaultVoltsPerDegreePerSecond = 0.007;
 void AnalogGyro::InitAnalogGyro(int channel) {
   SetPIDSourceType(PIDSourceType::kDisplacement);
 
-  std::stringstream ss;
-  ss << "analog/" << channel;
-  impl = new SimGyro(ss.str());
+  llvm::SmallString<128> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << "analog/" << channel;
+  impl = new SimGyro(oss.str());
 
   LiveWindow::GetInstance()->AddSensor("AnalogGyro", channel, this);
 }
diff --git a/wpilibc/sim/src/AnalogInput.cpp b/wpilibc/sim/src/AnalogInput.cpp
index 0c00b6e7b4..77191552d5 100644
--- a/wpilibc/sim/src/AnalogInput.cpp
+++ b/wpilibc/sim/src/AnalogInput.cpp
@@ -7,10 +7,10 @@
 
 #include "AnalogInput.h"
 
-#include <sstream>
-
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -20,9 +20,10 @@ using namespace frc;
  * @param channel The channel number to represent.
  */
 AnalogInput::AnalogInput(int channel) : m_channel(channel) {
-  std::stringstream ss;
-  ss << "analog/" << channel;
-  m_impl = new SimFloatInput(ss.str());
+  llvm::SmallString<32> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << "analog/" << channel;
+  m_impl = new SimFloatInput(oss.str());
 
   LiveWindow::GetInstance()->AddSensor("AnalogInput", channel, this);
 }
diff --git a/wpilibc/sim/src/DigitalInput.cpp b/wpilibc/sim/src/DigitalInput.cpp
index a560761b6f..4123d615c7 100644
--- a/wpilibc/sim/src/DigitalInput.cpp
+++ b/wpilibc/sim/src/DigitalInput.cpp
@@ -20,9 +20,9 @@ using namespace frc;
  * @param channel The digital channel (1..14).
  */
 DigitalInput::DigitalInput(int channel) : m_channel(channel) {
-  std::stringstream ss;
-  ss << "dio/" << channel;
-  m_impl = new SimDigitalInput(ss.str());
+  std::ostringstream oss;
+  oss << "dio/" << channel;
+  m_impl = new SimDigitalInput(oss.str());
 }
 
 /**
diff --git a/wpilibc/sim/src/DoubleSolenoid.cpp b/wpilibc/sim/src/DoubleSolenoid.cpp
index 1607dc8ff9..7ca3c273c5 100644
--- a/wpilibc/sim/src/DoubleSolenoid.cpp
+++ b/wpilibc/sim/src/DoubleSolenoid.cpp
@@ -9,6 +9,8 @@
 
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -37,10 +39,11 @@ DoubleSolenoid::DoubleSolenoid(int moduleNumber, int forwardChannel,
     forwardChannel = channel;
     m_reversed = true;
   }
-  std::stringstream ss;
-  ss << "pneumatic/" << moduleNumber << "/" << forwardChannel << "/"
-     << moduleNumber << "/" << reverseChannel;
-  m_impl = new SimContinuousOutput(ss.str());
+  llvm::SmallString<32> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << "pneumatic/" << moduleNumber << "/" << forwardChannel << "/"
+      << moduleNumber << "/" << reverseChannel;
+  m_impl = new SimContinuousOutput(oss.str());
 
   LiveWindow::GetInstance()->AddActuator("DoubleSolenoid", moduleNumber,
                                          forwardChannel, this);
diff --git a/wpilibc/sim/src/Encoder.cpp b/wpilibc/sim/src/Encoder.cpp
index cef4bef331..8f1d5dd4fe 100644
--- a/wpilibc/sim/src/Encoder.cpp
+++ b/wpilibc/sim/src/Encoder.cpp
@@ -7,10 +7,10 @@
 
 #include "Encoder.h"
 
-#include <sstream>
-
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -52,9 +52,10 @@ void Encoder::InitEncoder(int channelA, int channelB, bool reverseDirection,
   } else {
     m_reverseDirection = reverseDirection;
   }
-  std::stringstream ss;
-  ss << "dio/" << channelA << "/" << channelB;
-  impl = new SimEncoder(ss.str());
+  llvm::SmallString<32> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << "dio/" << channelA << "/" << channelB;
+  impl = new SimEncoder(oss.str());
   impl->Start();
 }
 
diff --git a/wpilibc/sim/src/MotorSafetyHelper.cpp b/wpilibc/sim/src/MotorSafetyHelper.cpp
index 83604d941f..be8a695c15 100644
--- a/wpilibc/sim/src/MotorSafetyHelper.cpp
+++ b/wpilibc/sim/src/MotorSafetyHelper.cpp
@@ -7,12 +7,12 @@
 
 #include "MotorSafetyHelper.h"
 
-#include <sstream>
-
 #include "DriverStation.h"
 #include "MotorSafety.h"
 #include "Timer.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -100,10 +100,11 @@ void MotorSafetyHelper::Check() {
 
   std::lock_guard<hal::priority_recursive_mutex> sync(m_syncMutex);
   if (m_stopTime < Timer::GetFPGATimestamp()) {
-    std::ostringstream desc;
+    llvm::SmallString<128> buf;
+    llvm::raw_svector_ostream desc(buf);
     m_safeObject->GetDescription(desc);
     desc << "... Output not updated often enough.";
-    wpi_setWPIErrorWithContext(Timeout, desc.str().c_str());
+    wpi_setWPIErrorWithContext(Timeout, desc.str());
     m_safeObject->StopMotor();
   }
 }
diff --git a/wpilibc/sim/src/PWM.cpp b/wpilibc/sim/src/PWM.cpp
index efdaae74a3..9c3f4342ee 100644
--- a/wpilibc/sim/src/PWM.cpp
+++ b/wpilibc/sim/src/PWM.cpp
@@ -7,10 +7,10 @@
 
 #include "PWM.h"
 
-#include <sstream>
-
 #include "Utility.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -30,16 +30,17 @@ const int PWM::kPwmDisabled = 0;
  *                port
  */
 PWM::PWM(int channel) {
-  std::stringstream ss;
+  llvm::SmallString<32> buf;
+  llvm::raw_svector_ostream oss(buf);
 
   if (!CheckPWMChannel(channel)) {
-    ss << "PWM Channel " << channel;
-    wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, ss.str());
+    oss << "PWM Channel " << channel;
+    wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, oss.str());
     return;
   }
 
-  ss << "pwm/" << channel;
-  impl = new SimContinuousOutput(ss.str());
+  oss << "pwm/" << channel;
+  impl = new SimContinuousOutput(oss.str());
   m_channel = channel;
   m_eliminateDeadband = false;
 
diff --git a/wpilibc/sim/src/Relay.cpp b/wpilibc/sim/src/Relay.cpp
index 898612a317..a44786fa67 100644
--- a/wpilibc/sim/src/Relay.cpp
+++ b/wpilibc/sim/src/Relay.cpp
@@ -7,11 +7,10 @@
 
 #include "Relay.h"
 
-#include <sstream>
-
 #include "LiveWindow/LiveWindow.h"
 #include "MotorSafetyHelper.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
 
 using namespace frc;
 
@@ -26,21 +25,22 @@ using namespace frc;
  */
 Relay::Relay(int channel, Relay::Direction direction)
     : m_channel(channel), m_direction(direction) {
-  std::stringstream ss;
+  llvm::SmallString<32> buf;
+  llvm::raw_svector_ostream oss(buf);
   if (!SensorBase::CheckRelayChannel(m_channel)) {
-    ss << "Relay Channel " << m_channel;
-    wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, ss.str());
+    oss << "Relay Channel " << m_channel;
+    wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, oss.str());
     return;
   }
 
   m_safetyHelper = std::make_unique<MotorSafetyHelper>(this);
   m_safetyHelper->SetSafetyEnabled(false);
 
-  ss << "relay/" << m_channel;
-  impl = new SimContinuousOutput(ss.str());  // TODO: Allow two different relays
-                                             // (targetting the different halves
-                                             // of a relay) to be combined to
-                                             // control one motor.
+  oss << "relay/" << m_channel;
+
+  // TODO: Allow two different relays (targetting the different halves of a
+  // relay) to be combined to control one motor.
+  impl = new SimContinuousOutput(oss.str());
   LiveWindow::GetInstance()->AddActuator("Relay", 1, m_channel, this);
   go_pos = go_neg = false;
 }
@@ -194,7 +194,7 @@ bool Relay::IsSafetyEnabled() const {
   return m_safetyHelper->IsSafetyEnabled();
 }
 
-void Relay::GetDescription(std::ostringstream& desc) const {
+void Relay::GetDescription(llvm::raw_ostream& desc) const {
   desc << "Relay " << GetChannel();
 }
 
diff --git a/wpilibc/sim/src/RobotDrive.cpp b/wpilibc/sim/src/RobotDrive.cpp
index cdcc994018..59f26bd538 100644
--- a/wpilibc/sim/src/RobotDrive.cpp
+++ b/wpilibc/sim/src/RobotDrive.cpp
@@ -715,7 +715,7 @@ void RobotDrive::SetSafetyEnabled(bool enabled) {
   // FIXME: m_safetyHelper->SetSafetyEnabled(enabled);
 }
 
-void RobotDrive::GetDescription(std::ostringstream& desc) const {
+void RobotDrive::GetDescription(llvm::raw_ostream& desc) const {
   desc << "RobotDrive";
 }
 
diff --git a/wpilibc/sim/src/SafePWM.cpp b/wpilibc/sim/src/SafePWM.cpp
index 4e42958f32..3217784041 100644
--- a/wpilibc/sim/src/SafePWM.cpp
+++ b/wpilibc/sim/src/SafePWM.cpp
@@ -8,7 +8,6 @@
 #include "SafePWM.h"
 
 #include <memory>
-#include <sstream>
 
 using namespace frc;
 
@@ -76,7 +75,7 @@ bool SafePWM::IsSafetyEnabled() const {
   return m_safetyHelper->IsSafetyEnabled();
 }
 
-void SafePWM::GetDescription(std::ostringstream& desc) const {
+void SafePWM::GetDescription(llvm::raw_ostream& desc) const {
   desc << "PWM " << GetChannel();
 }
 
diff --git a/wpilibc/sim/src/Solenoid.cpp b/wpilibc/sim/src/Solenoid.cpp
index ef19ffba9a..2ddb4bcf4c 100644
--- a/wpilibc/sim/src/Solenoid.cpp
+++ b/wpilibc/sim/src/Solenoid.cpp
@@ -7,10 +7,10 @@
 
 #include "Solenoid.h"
 
-#include <sstream>
-
 #include "LiveWindow/LiveWindow.h"
 #include "WPIErrors.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 #include "simulation/simTime.h"
 
 using namespace frc;
@@ -29,9 +29,10 @@ Solenoid::Solenoid(int channel) : Solenoid(1, channel) {}
  * @param channel      The channel on the solenoid module to control (1..8).
  */
 Solenoid::Solenoid(int moduleNumber, int channel) {
-  std::stringstream ss;
-  ss << "pneumatic/" << moduleNumber << "/" << channel;
-  m_impl = new SimContinuousOutput(ss.str());
+  llvm::SmallString<32> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << "pneumatic/" << moduleNumber << "/" << channel;
+  m_impl = new SimContinuousOutput(oss.str());
 
   LiveWindow::GetInstance()->AddActuator("Solenoid", moduleNumber, channel,
                                          this);
diff --git a/wpilibc/sim/src/Utility.cpp b/wpilibc/sim/src/Utility.cpp
index 1f386f9818..390e658d5d 100644
--- a/wpilibc/sim/src/Utility.cpp
+++ b/wpilibc/sim/src/Utility.cpp
@@ -15,10 +15,10 @@
 #include <cstdio>
 #include <cstdlib>
 #include <iostream>
-#include <sstream>
 
 #include "Timer.h"
 #include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 #include "simulation/simTime.h"
 
 using namespace frc;
@@ -61,7 +61,8 @@ bool wpi_assert_impl(bool conditionValue, llvm::StringRef conditionText,
                      llvm::StringRef message, llvm::StringRef fileName,
                      int lineNumber, llvm::StringRef funcName) {
   if (!conditionValue) {
-    std::stringstream errorStream;
+    llvm::SmallString<1024> errorBuf;
+    llvm::raw_svector_ostream errorStream(errorBuf);
 
     errorStream << "Assertion \"" << conditionText << "\" ";
     errorStream << "on line " << lineNumber << " ";
@@ -70,9 +71,9 @@ bool wpi_assert_impl(bool conditionValue, llvm::StringRef conditionText,
     errorStream << "of " << basename(fileName.c_str(fileTemp)) << " ";
 
     if (!message.empty()) {
-      errorStream << "failed: " << message << std::endl;
+      errorStream << "failed: " << message << "\n";
     } else {
-      errorStream << "failed." << std::endl;
+      errorStream << "failed.\n";
     }
 
     // Print to console and send to remote dashboard
@@ -94,7 +95,8 @@ void wpi_assertEqual_common_impl(int valueA, int valueB,
                                  llvm::StringRef fileName, int lineNumber,
                                  llvm::StringRef funcName) {
   // Error string buffer
-  std::stringstream error;
+  llvm::SmallString<1024> buf;
+  llvm::raw_svector_ostream error(buf);
 
   // If an error message was specified, include it
   // Build error string
@@ -192,12 +194,13 @@ std::string GetStackTrace(int offset) {
   void* stackTrace[128];
   int stackSize = backtrace(stackTrace, 128);
   char** mangledSymbols = backtrace_symbols(stackTrace, stackSize);
-  std::stringstream trace;
+  llvm::SmallString<1024> buf;
+  llvm::raw_svector_ostream trace(buf);
 
   for (int i = offset; i < stackSize; i++) {
     // Only print recursive functions once in a row.
     if (i == 0 || stackTrace[i] != stackTrace[i - 1]) {
-      trace << "\tat " << demangle(mangledSymbols[i]) << std::endl;
+      trace << "\tat " << demangle(mangledSymbols[i]) << "\n";
     }
   }
 
diff --git a/wpilibj/src/athena/cpp/lib/CANJNI.cpp b/wpilibj/src/athena/cpp/lib/CANJNI.cpp
index 94a381198a..2a7ec77867 100644
--- a/wpilibj/src/athena/cpp/lib/CANJNI.cpp
+++ b/wpilibj/src/athena/cpp/lib/CANJNI.cpp
@@ -7,13 +7,14 @@
 
 #include <assert.h>
 #include <jni.h>
-#include "HAL/cpp/Log.h"
-
-#include "edu_wpi_first_wpilibj_can_CANJNI.h"
 
 #include "FRC_NetworkCommunication/CANSessionMux.h"
 #include "HAL/CAN.h"
+#include "HAL/cpp/Log.h"
 #include "HALUtil.h"
+#include "edu_wpi_first_wpilibj_can_CANJNI.h"
+#include "llvm/SmallString.h"
+#include "llvm/raw_ostream.h"
 
 using namespace frc;
 
@@ -44,14 +45,15 @@ Java_edu_wpi_first_wpilibj_can_CANJNI_FRCNetCommCANSessionMuxSendMessage(
       (uint8_t *)(data ? env->GetDirectBufferAddress(data) : 0);
   uint8_t dataSize = (uint8_t)(data ? env->GetDirectBufferCapacity(data) : 0);
 
-  CANJNI_LOG(logDEBUG) << "Message ID " << std::hex << messageID;
+  CANJNI_LOG(logDEBUG) << "Message ID ";
+  CANJNI_LOG(logDEBUG).write_hex(messageID);
 
   if (logDEBUG <= canJNILogLevel) {
     if (dataBuffer) {
-      std::ostringstream str;
-      str << std::setfill('0') << std::hex;
+      llvm::SmallString<128> buf;
+      llvm::raw_svector_ostream str(buf);
       for (int32_t i = 0; i < dataSize; i++) {
-        str << std::setw(2) << (int)dataBuffer[i] << ' ';
+        str.write_hex(dataBuffer[i]) << ' ';
       }
 
       Log().Get(logDEBUG) << "Data: " << str.str();
@@ -93,13 +95,20 @@ Java_edu_wpi_first_wpilibj_can_CANJNI_FRCNetCommCANSessionMuxReceiveMessage(
   FRC_NetworkCommunication_CANSessionMux_receiveMessage(
       messageIDPtr, messageIDMask, buffer, &dataSize, timeStampPtr, &status);
 
-  CANJNI_LOG(logDEBUG) << "Message ID " << std::hex << *messageIDPtr;
+  CANJNI_LOG(logDEBUG) << "Message ID ";
+  CANJNI_LOG(logDEBUG).write_hex(*messageIDPtr);
 
   if (logDEBUG <= canJNILogLevel) {
-    std::ostringstream str;
-    str << std::setfill('0') << std::hex;
+    llvm::SmallString<128> buf;
+    llvm::raw_svector_ostream str(buf);
+
     for (int32_t i = 0; i < dataSize; i++) {
-      str << std::setw(2) << (int)buffer[i] << ' ';
+      // Pad one-digit data with a zero
+      if (buffer[i] <= 16) {
+        str << '0';
+      }
+
+      str.write_hex(buffer[i]) << ' ';
     }
 
     Log().Get(logDEBUG) << "Data: " << str.str();
diff --git a/wpilibj/src/athena/cpp/lib/HALUtil.cpp b/wpilibj/src/athena/cpp/lib/HALUtil.cpp
index a06daeb8c8..5ad1e53293 100644
--- a/wpilibj/src/athena/cpp/lib/HALUtil.cpp
+++ b/wpilibj/src/athena/cpp/lib/HALUtil.cpp
@@ -59,20 +59,21 @@ namespace frc {
 void ThrowAllocationException(JNIEnv *env, int32_t minRange, int32_t maxRange, 
     int32_t requestedValue, int32_t status) {
   const char *message = HAL_GetErrorMessage(status);
-  char *buf = new char[strlen(message) + 100];
-  sprintf(buf, 
-      " Code: $%d. %s, Minimum Value: %d, Maximum Value: %d, Requested Value: %d", 
-      status, message, minRange, maxRange, requestedValue);
-  allocationExCls.Throw(env, buf);
-  delete[] buf;
+  llvm::SmallString<1024> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << " Code: " << status << ". " << message << ", Minimum Value: "
+      << minRange << ", Maximum Value: " << maxRange << ", Requested Value: "
+      << requestedValue;
+  env->ThrowNew(allocationExCls, buf.c_str());
+  allocationExCls.Throw(env, buf.c_str());
 }
 
 void ThrowHalHandleException(JNIEnv *env, int32_t status) {
   const char *message = HAL_GetErrorMessage(status);
-  char *buf = new char[strlen(message) + 30];
-  sprintf(buf, " Code: $%d. %s", status, message);
-  halHandleExCls.Throw(env, buf);
-  delete[] buf;
+  llvm::SmallString<1024> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << " Code: " << status << ". " << message;
+  halHandleExCls.Throw(env, buf.c_str());
 }
 
 constexpr const char wpilibjPrefix[] = "edu.wpi.first.wpilibj";  
@@ -84,10 +85,10 @@ void ReportError(JNIEnv *env, int32_t status, bool do_throw) {
   }
   const char *message = HAL_GetErrorMessage(status);
   if (do_throw && status < 0) {
-    char *buf = new char[strlen(message) + 30];
-    sprintf(buf, " Code: %d. %s", status, message);
-    runtimeExCls.Throw(env, buf);
-    delete[] buf;
+    llvm::SmallString<1024> buf;
+    llvm::raw_svector_ostream oss(buf);
+    oss << " Code: " << status << ". " << message;
+    runtimeExCls.Throw(env, buf.c_str());
   } else {
     std::string func;
     auto stack = GetJavaStackTrace<wpilibjPrefix>(env, &func);
@@ -107,10 +108,10 @@ void ThrowError(JNIEnv *env, int32_t status, int32_t minRange, int32_t maxRange,
     ThrowHalHandleException(env, status);
   }
   const char *message = HAL_GetErrorMessage(status);
-  char *buf = new char[strlen(message) + 30];
-  sprintf(buf, " Code: %d. %s", status, message);
-  runtimeExCls.Throw(env, buf);
-  delete[] buf;
+  llvm::SmallString<1024> buf;
+  llvm::raw_svector_ostream oss(buf);
+  oss << " Code: " << status << ". " << message;
+  runtimeExCls.Throw(env, buf.c_str());
 }
 
 void ReportCANError(JNIEnv *env, int32_t status, int message_id) {
@@ -143,9 +144,10 @@ void ReportCANError(JNIEnv *env, int32_t status, int message_id) {
     }
     case ERR_CANSessionMux_NotAllowed:
     case kRIOStatusFeatureNotSupported: {
-      char buf[100];
-      sprintf(buf, "MessageID = %d", message_id);
-      canMessageNotAllowedExCls.Throw(env, buf);
+      llvm::SmallString<100> buf;
+      llvm::raw_svector_ostream oss(buf);
+      oss << "MessageID = " << message_id;
+      canMessageNotAllowedExCls.Throw(env, buf.c_str());
       break;
     }
     case ERR_CANSessionMux_NotInitialized:
@@ -160,9 +162,10 @@ void ReportCANError(JNIEnv *env, int32_t status, int message_id) {
       break;
     }
     default: {
-      char buf[100];
-      sprintf(buf, "Fatal status code detected: %d", status);
-      uncleanStatusExCls.Throw(env, buf);
+      llvm::SmallString<100> buf;
+      llvm::raw_svector_ostream oss(buf);
+      oss << "Fatal status code detected: " << status;
+      uncleanStatusExCls.Throw(env, buf.c_str());
       break;
     }
   }