在创建 AVR Studio 5 项目时，它会创建一个包含以下内容的 .c 文件：
#include <avr/io.h>
int main(void)
{
while(1)
{
//TODO:: Please write your application code
}
}
编译这个C程序没有问题：
------ Rebuild All started: Project: AVRGCC2, Configuration: Debug AVR ------
Build started.
Project "AVRGCC2.avrgccproj" (ReBuild target(s)):
Target "PreBuildEvent" skipped, due to false condition; ('$(PreBuildEvent)'!='') was evaluated as (''!='').
Target "CoreRebuild" in file "C:\Programme\Atmel\AVR Studio 5.0\Vs\AvrGCC.targets" from project "C:\Dokumente und Einstellungen\tom\Eigene Dateien\AVRStudio\test\AVRGCC2\AVRGCC2\AVRGCC2.avrgccproj" (target "ReBuild" depends on it):
Task "RunAvrGCC"
C:\Programme\Atmel\AVR Studio 5.0\AVR ToolChain\bin\make.exe clean all
rm -rf AVRGCC2.o AVRGCC2.d libAVRGCC2.a AVRGCC2.hex AVRGCC2.eep AVRGCC2.lss AVRGCC2.map
AVRGCC2.c
Invoking: AVR/GNU C Compiler
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-gcc.exe" -funsigned-char -funsigned-bitfields -O0 -fpack-struct -fshort-enums -g2 -Wall -c -std=gnu99 -mmcu=atmega328p -MD -MP -MF"AVRGCC2.d" -MT"AVRGCC2.d" -o"AVRGCC2.o" ".././AVRGCC2.c"
Finished building: .././AVRGCC2.c
Building target: AVRGCC2.elf
Invoking: AVR/GNU C/C++ Linker
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-gcc.exe" -mmcu=atmega328p -Wl,-Map=AVRGCC2.map -o AVRGCC2.elf AVRGCC2.o
Finished building target: AVRGCC2.elf
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-objcopy.exe" -O ihex -R .eeprom -R .fuse -R .lock -R .signature "AVRGCC2.elf" "AVRGCC2.hex"
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-objdump.exe" -h -S "AVRGCC2.elf" > "AVRGCC2.lss"
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-objcopy.exe" -j .eeprom --set-section-flags=.eeprom=alloc,load --change-section-lma .eeprom=0 --no-change-warnings -O ihex "AVRGCC2.elf" "AVRGCC2.eep" || exit 0
AVR Memory Usage
----------------
Device: atmega328p
Program: 142 bytes (0.4% Full)
(.text + .data + .bootloader)
Data: 0 bytes (0.0% Full)
(.data + .bss + .noinit)
Done executing task "RunAvrGCC".
Done building target "CoreRebuild" in project "AVRGCC2.avrgccproj".
Target "PostBuildEvent" skipped, due to false condition; ('$(PostBuildEvent)' != '') was evaluated as ('' != '').
Target "ReBuild" in file "C:\Programme\Atmel\AVR Studio 5.0\Vs\Avr.common.targets" from project "C:\Dokumente und Einstellungen\tom\Eigene Dateien\AVRStudio\test\AVRGCC2\AVRGCC2\AVRGCC2.avrgccproj" (entry point):
Done building target "ReBuild" in project "AVRGCC2.avrgccproj".
Done building project "AVRGCC2.avrgccproj".
Build succeeded.
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========
但是，当我将文件扩展名更改为 .cpp 后，构建过程会发出警告设备类型未定义（如果尝试使用任何 AVR 特定寄存器，则此警告将变成错误）：
------ Rebuild All started: Project: AVRGCC2, Configuration: Debug AVR ------
Build started.
Project "AVRGCC2.avrgccproj" (ReBuild target(s)):
Target "PreBuildEvent" skipped, due to false condition; ('$(PreBuildEvent)'!='') was evaluated as (''!='').
Target "CoreRebuild" in file "C:\Programme\Atmel\AVR Studio 5.0\Vs\AvrGCC.targets" from project "C:\Dokumente und Einstellungen\tom\Eigene Dateien\AVRStudio\test\AVRGCC2\AVRGCC2\AVRGCC2.avrgccproj" (target "ReBuild" depends on it):
Task "RunAvrGCC"
C:\Programme\Atmel\AVR Studio 5.0\AVR ToolChain\bin\make.exe clean all
In file included from .././AVRGCC2.cpp:1:0:
c:\programme\atmel\avr studio 5.0\avr toolchain\bin\../lib/gcc/avr/4.5.1/../../../../avr/include/avr/io.h(446,6): #warning "device type not defined"
rm -rf AVRGCC2.o AVRGCC2.d libAVRGCC2.a AVRGCC2.hex AVRGCC2.eep AVRGCC2.lss AVRGCC2.map
AVRGCC2.cpp
Invoking: AVR/GNU CPP Compiler
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-g++.exe" -MD -MP -MF"AVRGCC2.d" -MT"AVRGCC2.d" -o"AVRGCC2.o" ".././AVRGCC2.cpp"
Finished building: .././AVRGCC2.cpp
Building target: AVRGCC2.elf
Invoking: AVR/GNU C/C++ Linker
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-gcc.exe" -mmcu=atmega328p -Wl,-Map=AVRGCC2.map -o AVRGCC2.elf AVRGCC2.o
Finished building target: AVRGCC2.elf
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-objcopy.exe" -O ihex -R .eeprom -R .fuse -R .lock -R .signature "AVRGCC2.elf" "AVRGCC2.hex"
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-objdump.exe" -h -S "AVRGCC2.elf" > "AVRGCC2.lss"
"C:/Programme/Atmel/AVR Studio 5.0/AVR ToolChain/bin/avr-objcopy.exe" -j .eeprom --set-section-flags=.eeprom=alloc,load --change-section-lma .eeprom=0 --no-change-warnings -O ihex "AVRGCC2.elf" "AVRGCC2.eep" || exit 0
AVR Memory Usage
----------------
Device: atmega328p
Program: 142 bytes (0.4% Full)
(.text + .data + .bootloader)
Data: 0 bytes (0.0% Full)
(.data + .bss + .noinit)
Done executing task "RunAvrGCC".
Done building target "CoreRebuild" in project "AVRGCC2.avrgccproj".
Target "PostBuildEvent" skipped, due to false condition; ('$(PostBuildEvent)' != '') was evaluated as ('' != '').
Target "ReBuild" in file "C:\Programme\Atmel\AVR Studio 5.0\Vs\Avr.common.targets" from project "C:\Dokumente und Einstellungen\tom\Eigene Dateien\AVRStudio\test\AVRGCC2\AVRGCC2\AVRGCC2.avrgccproj" (entry point):
Done building target "ReBuild" in project "AVRGCC2.avrgccproj".
Done building project "AVRGCC2.avrgccproj".
Build succeeded.
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========
比较这两个输出结果可以发现，对于C代码，它会在执行avr-gcc.exe时添加选项-mmcu=atmega328p，但对于C++代码则不会。在使用WinAVR时也遇到了类似的问题。该如何解决？
-x c++ -std=gnu++98。 - Mot