Question

Possible Duplicate:
Why is a C/C++ “Hello World” in the kilobytes?

Consider the following program written in ANSI C.

file: test.c
main() {}

I’m on Windows 7. I use MinGW to compile this file.

$ gcc test.c

Then, I want to see the size of this file.

$ ls -la a.exe
-rwxr-xr-x 1 Username Administrators 47902 Nov 21 15:57 a.exe

It appears that this completely empty, worthless C program compiles to a binary that is almost fifty kilobytes in size. Why in the world is this happening?

Answer 1

Run GCC like gcc -v test.c. The GCC (the compiler driver) spawns cc1 (the compiler), as (the assembler) and ld (the linker). Look at the linker command line and you’ll see several files (something like crti.o, crt0.o, crtbegin.o, crtend.o, etc.) linked in the final executable. ANd some of them may fetch symbols from libgcc.a or libc.a. That explains why the size is not just a few bytes.

You could also run it with -Wl,-Map=map.txt to generate a map file, which will reveal every function or variable from every object and library, which is included in the final executable.