windows c compiler generating large executables

Question

I was writing a c program for windows, and compiling it with: cl test.c and I noticed that the file size was 95744 bytes.

I thought that was strange so I began shortening the program to see if that would affect the size of the executable, but it stayed the same, I eventually just compiled an empty main function, with the same result, I attempted the same program on wsl2, compiling it with gcc test.c -o test and ran size on the elf which outputted:

   text    data     bss     dec     hex filename
   1224     544       8    1776     6f0 test

does anyone know why this is or how to make the output smaller?

any help is greatly appreciated.

Try adding `-O3` or `-Os` flags, enabling optimisations, the former for speed (but still reduces size), the latter for size explicitly (but still affects speed). — Aconcagua, Jun 19 '23 at 16:45
I'm attempting to make the windows executable smaller not the elf, sorry if that was unclear. — Bernard Putnam Sproul, Jun 19 '23 at 16:49
Does this answer your question? [How to reduce the size of executable produced by MinGW g++ compiler?](https://stackoverflow.com/questions/7973274/how-to-reduce-the-size-of-executable-produced-by-mingw-g-compiler) — Raymond Chen, Jun 19 '23 at 16:49
debug symbols - only link to pdb. maximum ~100h bytes. this is static linked crt — RbMm, Jun 19 '23 at 16:50
@RaymondChen No, I'm using the cl command in developer powershell. — Bernard Putnam Sproul, Jun 19 '23 at 16:51
@12431234123412341234123 No, I'm not trying to reduce the file size on wsl, just on windows. — Bernard Putnam Sproul, Jun 19 '23 at 16:54
Try `/MD` for dynamically linked libc and `/O2` for optimization. — Jason, Jun 19 '23 at 16:56
@Jason, /MD reduced the size of the output file down to 9216 bytes, could you post it as an answer so I can accept it? — Bernard Putnam Sproul, Jun 19 '23 at 17:00

score 4 · Accepted Answer · answered Jun 19 '23 at 17:03

4

The issue is that cl.exe is statically linking libc by default meaning the C runtime library will be embedded into your executable. That is where the bulk of the file size is coming from. The option /MD will do a dynamic linking so these functions can be found at runtime.

Also, optimization options like /O2 will also help to reduce the size of the resulting executable.

answered Jun 19 '23 at 17:03

Jason

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`/O2` does speed optimization. It'll reduce some space wasted for debugging purposes but it definitely won't produce binaries as small as `/Os`. But `/O2` or `/Ox` should be the default, not `/Os` – phuclv Jun 19 '23 at 17:10
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@phuclv True. The implication being any optimization at all will be smaller than the default options. – Jason Jun 19 '23 at 17:20

windows c compiler generating large executables

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