I am trying to learn assembly language. I have searched and found how to disassemble a .c file but I think it produces some optimized version of the program. Is there any way so that I can see the exact assembly code which corresponds to my C file.
This question is related to
c
gcc
compiler-optimization
compiler-options
You can disable optimizations if you pass -O0 with the gcc command-line.
E.g. to turn a .C file into a .S file call:
gcc -O0 -S test.c
To test without copy elision and see you copy/move constructors/operators in action add "-fno-elide-constructors".
Even with no optimizations (-O0 ), GCC and Clang will still do copy elision, which has the effect of skipping copy/move constructors in some cases. See this question for the details about copy elision.
However, in Clang 3.4 it does trigger a bug (an invalid temporary object without calling constructor), which is fixed in 3.5.
Use the command-line option -O0 (-[capital o][zero]) to disable optimization, and -S to get assembly file. Look here to see more gcc command-line options.
For gcc you want to omit any -O1 -O2 or -O3 options passed to the compiler or if you already have them you can append the -O0 option to turn it off again. It might also help you to add -g for debug so that you can see the c source and disassembled machine code in your debugger.
See also: http://sourceware.org/gdb/onlinedocs/gdb/Optimized-Code.html
Long time ago, but still needed.
info - https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
list - gcc -Q --help=optimizers test.c | grep enabled
disable as many as you like with:
gcc **-fno-web** -Q --help=optimizers test.c | grep enabled
You can also control optimisations internally with #pragma GCC push_options
#pragma GCC push_options
/* #pragma GCC optimize ("unroll-loops") */
.... code here .....
#pragma GCC pop_options
Source: Stackoverflow.com