#pragma GCC diagnostic ignored "-Wunused-parameter"和#pragma GCC diagnostic ignored "-Wdeprecated-declarations"極其有用

Suppressing Warnings in GCC and Clang (nelkinda.com)

GCC Command Line Options 下面列出一些有趣的：

--help={target|optimizers|warnings|params|[^]{joined|separate|undocumented}}[,...] Display specific types of command line options
-dumpspecs               Display all of the built in spec strings
-print-search-dirs       Display the directories in the compiler's search path
-print-sysroot           Display the target libraries directory
-pipe                    Use pipes rather than intermediate files
-time                    Time the execution of each subprocess
--sysroot=<directory>    Use <directory> as the root directory for headers and libraries
-B <directory>           Add <directory> to the compiler's search paths
-v                       Display the programs invoked by the compiler
-E                       Preprocess only; do not compile, assemble or link
-S                       Compile only; do not assemble or link
-m128bit-long-double        sizeof(long double) is 16
-m96bit-long-double         sizeof(long double) is 12
-m32                        Generate 32bit i386 code
-m3dnow                     Support 3DNow! built-in functions
-m3dnowa                    Support Athlon 3Dnow! built-in functions
-m64                        Generate 64bit x86-64 code
-mabm                       Support code generation of Advanced Bit Manipulation (ABM) instructions.
-mavx                       Support MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2 and AVX built-in functions and code generation
-mwin32                     Set Windows defines
-mwindows                   Create GUI application
-fPIC                       Generate position-independent code if possible (large mode)
-fPIE                       Generate position-independent code for executables if possible (large mode)
-pie                        Create a position independent executable
-shared                     Create a shared library
-g                          Generate debug information in default format
-ggdb                       Generate debug information in default extended format
-p                          Enable function profiling
-O<number>                  Set optimization level to <number>
-Os                         Optimize for space rather than speed
-Ofast                      Disregard strict standards compliance. -Ofast enables all -O3 optimizations.

Optimize Options (Using the GNU Compiler Collection (GCC)) 沒有-O4，最高就是3: