CODEWITHSUNDEEP
cgccassemblytoolchain
Black.Jack
Black.Jack

Reputation: 1959

How to use asm procedure and take return value in C

i've got a gcc version 2.95.2 19991024 (release) toolchain and now i need to use an Assembly function that is in a file positioned in the same folder of the makefile.

I've tried tons of ways to put that file in my toolchain, with no luck.

Basically i declare that in ASM:

.globl  util_MyFunc
util_MyFunc: 
...

And in the main void of C file:

extern void util_MyFunc();
int main(void) {  
 util_MyFunc();
...

When i compile i got the error related to not recognized:

/cygdrive/c/MyDev/tmp/main.o(.text+0x8bc): undefined reference to `util_MyFunc'
make: *** [test.o] Error 1

Thanks!

EDIT:

i've tried to use following to generate the ".o" file from the asm file

C:\MyDev>gcc -c test.asm -o test.o

It results:

gcc: utils.asm: linker input file unused since linking not done

or:

C:\MyDev>gcc test.asm -o test.o

but...:

ld: cannot open crt0.o: No such file or directory

Upvotes: 0

Views: 356

Answers (1)

Jester
Jester

Reputation: 58762

The canonical extension for assembly files that gcc expects is .s. You should use that (or assemble using as directly). Also possibly put the -o test.o before the input file name. Finally, you will need libc development files if you want to use libc. Otherwise use -nostdlib switch.

You should try: gcc -o test main.c utils.s

Upvotes: 2

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