printf and puts problem...

[AlfaOmega08]

In the main function of my os, I've writed:

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printf("printf test\n");
printf("String: %s", "Hello World!");
printf("Signed: %d & %d", 20, -20);
printf("Unsigned: %u", -20);
printf("Hex: %x", 255);

When linking, ld exit with the error:
undefined reference to 'puts'

if i write

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pritnf("\n");

there is an undefined reference to 'putchar'

Maybe GCC excange printf with putchar or puts?[/code]

[Wave]

Where do you define printf()?

[xyjamepa]

Maybe GCC excange printf with putchar or puts?

No,

undefined reference to 'puts'

means GCC can't find puts,so you should include the file which you've defined puts in it.

[AlfaOmega08]

I've defined it in stdio.h as
int printf(const char *format, ...);

then in stdio.c there is the source

but the error is from another source file where the call is

[AlfaOmega08]

undefined reference to 'puts'

means GCC can't find puts,so you should include the file which you've defined puts in it.

I know. But first I've a video::puts function, not a puts function, and second, there isn't any reference to puts in the source file

[proxy]

GCC does do basic function substitution when certain optimizations are enabled. For example.

printf("a"); -> putchar('a');
printf("hello\n") -> puts("hello");

basically if there is no format character in the string then it may be reduced to a simpler function.

proxy

[AlfaOmega08]

GCC does do basic function substitution when certain optimizations are enabled

how can I disable that optimizations?

[lukem95]

using the -O argument you can control the optimisation level.

-O0 is none.

[Ready4Dis]

Also, make sure you are compiling as "free standing", so it's not trying to use the actual printf made for something other than your operating system.

[skyking]

Actually it's -fno-builtin that does the trick...

And -nostdlib to avoid linking with the libraries used on the OS that gcc is on (or -nodefaultlibs to avoid gcc provided library functions).

[Ready4Dis]

Actually it's -fno-builtin that does the trick...

And -nostdlib to avoid linking with the libraries used on the OS that gcc is on (or -nodefaultlibs to avoid gcc provided library functions).

Hmm.. the only things I use are:
-fno-leading-underscore -ffreestanding -fpack-struct

I don't want the leading underscore, since it makes my C -> asm easier (as well as linking libraries), freestanding was so it doesn't link the regular C library (or so I thought, and it works for me, so i dunno), and pack-struct because I wanted all my structures packed unless I specifically tell it not to be (so I am 100% positive my structs are what I think they are, and if I compile for 64-bit I don't want it all breaking unless I already know it's going to). Anyways, those are the only arguments I use for gcc and my kernel and drivers compile without issue.

[skyking]

Actually it's -fno-builtin that does the trick...

And -nostdlib to avoid linking with the libraries used on the OS that gcc is on (or -nodefaultlibs to avoid gcc provided library functions).

Hmm.. the only things I use are:
-fno-leading-underscore -ffreestanding -fpack-struct

I don't want the leading underscore, since it makes my C -> asm easier (as well as linking libraries), freestanding was so it doesn't link the regular C library (or so I thought, and it works for me, so i dunno), and pack-struct because I wanted all my structures packed unless I specifically tell it not to be (so I am 100% positive my structs are what I think they are, and if I compile for 64-bit I don't want it all breaking unless I already know it's going to). Anyways, those are the only arguments I use for gcc and my kernel and drivers compile without issue.

Yes there are different ways things can be done. -O0 is however none of them in this case...