A useful list of gcc compiler options

Useful GCC Compiler Options.md

Useful GCC Compiler Options

A non exhaustive list of gcc compiler options.

$ gcc myprog.c -o myprog -Wall -Wextra -pedantic -std=c11 [...]

Optimization:

Options	Details
-O0	explicitly turns off all optimizations.
-O1	enables a few optimizations, but isn't very useful overall.
-O2	is the most commonly used optimization flag.
-O3	enable even more optimizations, but can actually harm the runtime of your code by making it take up more space (so it doesn't fit into cache anymore).
-Os	optimizes for small binaries.

Warnings/errors:

Options	Details
-Wall	enables some warnings.
-Wextra	enables more warnings.
-pedantic	will try to enforce standards compliance.
-Werror	turns warnings into errors.

NOTES: You can turn individual warnings on/off with -Wthis-warning or -Wno-this-warning.

Debugging:

Options	Details
-C	Produce only the compiled code
-g	adds debug symbols.
-fsanitize=address	Enable AddressSanitizer, a fast memory error detector.
-fsanitize=pointer-compare	Ensure that their's no comparasson between two pointers from different objects using the relational operators. The option must be combined with -fsanitize=address
-march=native -mtune=native	enables optimizations which work specifically on your cpu and might not on others.
-m32	makes a 32-bit object rather than a 64-bit one (assuming your processor is 64-bit)
-fPIC	makes position independent code. (usefull to make a shared library)
-fPIE	makes position independent executable (usefull to make security-critical code)
-S	generate assembly code instead of object files. Useful for seeing what the compiler is doing, and gaining insights into how the code could be optimized.
-E	produce only the preprocessor output

Miscellaneous:

Options	Details
-Idirectory	look for header files in this location
-Dfoo[=bar]	compile time macro: same as saying #define foo [bar] in your source file
-std=[c89, c99, c11, c17, gnu-x]	enforces compliance to a given version of c.
-Lwhatever	adds whatever to the library search dir (so if you do gcc -Lwhatever -lbla, you might link to whatever/libbla.so).

Credits

Thanks to reddit users u/5tarrealm5, u/Elronnd, u/maep and u/capilot for inspiring this notes.

Please note that this gist has not been updated since 6 years ago.
Maybe, one day, I'll update it, but for the moment please check the -fsanitize flag.
It's now an essentials.