当我使用gcc编译一个非常简单的源文件时，我不必指定标准包含文件的路径，例如stdio或stdlib。
GCC如何知道如何找到这些文件？
它内部是否有/usr/include路径硬连线，还是从其他操作系统组件获取路径？
答案 0 :(得分：146)
为了找出gcc / g++使用的默认路径及其优先级，您需要检查以下命令的输出：
gcc -xc -E -v -
gcc -xc++ -E -v -
归功于 Qt Creator团队 。
答案 1 :(得分：30)
有一个输出较短的命令，允许从一行开始自动剪切包含的包含：
$ echo | gcc -Wp,-v -x c++ - -fsyntax-only
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/4.8.2/include-fixed"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/x86_64-redhat-linux
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../include/c++/4.8.2/backward
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/include
/usr/local/include
/usr/include
End of search list.
归功于libc ++ front-page。
答案 2 :(得分：2)
以下是一篇描述gcc搜索路径的文章：http://www.network-theory.co.uk/docs/gccintro/gccintro_21.html
此外，您可以使用-I开关指定额外的搜索路径。您可以从命令行或makefile中执行此操作。
答案 3 :(得分：0)
只需运行以下命令以列出默认搜索路径：
$（gcc -print-prog-name = cc1）-v
答案 4 :(得分：0)
尽管我同意Ihor Kaharlichenko关于考虑C ++的回答，也同意abyss.7关于其输出紧凑性的回答，但对于gcc的多体系结构版本，它们仍然不完整，因为输入处理取决于命令行参数和宏。
示例：
echo | /opt/gcc-arm-none-eabi-9-2019-q4-major/bin/arm-none-eabi-g++ -specs=nano.specs -mcpu=cortex-m4 -march=armv7e-m -mthumb -mfloat-abi=soft -x c++ -E -Wp,-v\
- -fsyntax-only产生
⋮
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../arm-none-eabi/include/newlib-nano
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include/c++/9.2.1
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include/c++/9.2.1/arm-none-eabi/thumb/v7e-m/nofp
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include/c++/9.2.1/backward
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/include
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/include-fixed
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include
⋮
echo | /opt/gcc-arm-none-eabi-9-2019-q4-major/bin/arm-none-eabi-g++ -x c++ -E -Wp,-v - -fsyntax-only产生
⋮
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include/c++/9.2.1
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include/c++/9.2.1/arm-none-eabi
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include/c++/9.2.1/backward
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/include
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/include-fixed
/opt/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/include
⋮
前一个调用使用newlib（请参见输出的第1和3行），后者使用标准include。列表末尾的公用文件是使用include_next的示例。
底线：打印包含目录时，请始终考虑所有宏和编译器选项。