How Can I Get Assembly Code Output from GCC Compiling C/C Source Code?

Getting Assembler Output from C/C Source in GCC

To analyze how code is compiled, it's beneficial to retrieve the emitted assembly code. In GCC, this can be achieved using the -S option.

gcc -S helloworld.c

This will invoke the preprocessor and initial compilation, but halt before running the assembler.

For more comprehensive assembly output, consider using -fverbose-asm alongside -O0. However, note that this works best at default optimization levels.

The default output file is helloworld.s, but can be customized using -o. Additionally, -o - can be used to direct output directly to standard output.

gcc -S -o my_asm_output.s helloworld.c

If only the object file is available, objdump with the --disassemble option can be employed:

objdump -S --disassemble helloworld > helloworld.dump

This will interleave source lines with disassembly output. Enabling debugging (-g) and avoiding stripping can enhance the disassembly details.

For even more customization, consider options such as -rwC (symbol relocations), -Mintel (Intel syntax), and -r (important for object files with placeholder symbol references).

For instance, the following command provides a detailed dump using Intel syntax:

objdump -drwC -Mintel -S foo.o | less

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