查看gcc build-in specs
gcc -dumpspecs
-dumpspecs
Print the compiler's built-in specs---and don't do anything else. (This is used when GCC itself is being built.)
看gcc到哪些目录查找头文件：
gcc -print-search-dirs
-print-search-dirs
Print the name of the configured installation directory and a list of program and library directories gcc will search---and don't do anything else.
This is useful when gcc prints the error message installation problem, cannot exec cpp0: No such file or directory. To resolve this you either need to put cpp0 and the other compiler components where gcc expects to find them, or you can set the environment variable
GCC_EXEC_PREFIX to the directory where you installed them. Don't forget the trailing /.
看gcc编译到那个平台
gcc -Q -v
-Q Makes the compiler print out each function name as it is compiled, and print some statistics about each pass when it finishes.
zhanxw@host10-41.sph.umich.edu: ~/temp> gcc -Q -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/x86_64-apple-darwin10/4.7.1/lto-wrapper
Target: x86_64-apple-darwin10
Configured with: ../gcc-4.7.1/configure --prefix=/opt/local --build=x86_64-apple-darwin10 --enable-languages=c,c++,objc,obj-c++,lto,fortran,java --libdir=/opt/local/lib/gcc47 --includedir=/opt/local/include/gcc47 --infodir=/opt/local/share/info --mandir=/opt/local/share/man --datarootdir=/opt/local/share/gcc-4.7 --with-libiconv-prefix=/opt/local --with-local-prefix=/opt/local --with-system-zlib --disable-nls --program-suffix=-mp-4.7 --with-gxx-include-dir=/opt/local/include/gcc47/c++/ --with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local --with-ppl=/opt/local --with-cloog=/opt/local --enable-cloog-backend=isl --enable-stage1-checking --disable-multilib --enable-lto --with-as=/opt/local/bin/as --with-ld=/opt/local/bin/ld --with-ar=/opt/local/bin/ar --with-bugurl=https://trac.macports.org/newticket --disable-ppl-version-check --with-pkgversion='MacPorts gcc47 4.7.1_2'
Thread model: posix
gcc version 4.7.1 (MacPorts gcc47 4.7.1_2)
看gcc默认开启了哪些FLAG（定义了哪些macro）
$cpp -dM <(echo "")
#define __DBL_MIN_EXP__ (-1021)
#define __FLT_MIN__ 1.17549435e-38F
#define __DEC64_DEN__ 0.000000000000001E-383DD
#define __CHAR_BIT__ 8
#define __WCHAR_MAX__ 2147483647
#define __DBL_DENORM_MIN__ 4.9406564584124654e-324
#define __FLT_EVAL_METHOD__ 0
#define __DBL_MIN_10_EXP__ (-307)
#define __FINITE_MATH_ONLY__ 0
#define __DEC64_MAX_EXP__ 384
...
...
和MacPorts 相关的——如何选择gcc
sudo port select --list gcc
sudo port select --set gcc gcc42 # default gcc in Mac Snow Leopard
sudo port select --set gcc mp-gcc47 # MacPorts GNU GCC 4.7
其他参考
【1】StackOverflow上的讨论：哪个macro可以区分Mac和Linux Link
【2】SourceForge上Pre-defined C/C++ Compiler Macros，包括以下方面：
Standards
Compilers
Libraries
Operating Systems
Architectures
Devices
Link