Do we need to add the fno-builtin compile option?

[prime-zeng]

We can't use gcc builtin function in OP-TEE(TAs)， so if we don't have the fno-builtin option, an linker error will be reported if we use the builtin functions by mistake, but i 'd rather to have this option and then report a compile error instead, any idea?

[jforissier]

Hi @prime-zeng,

What do you mean? Do you have an example? (I suspect -fno-builtin is not the option you need but I want to make sure what problem you're trying to fix).

[jforissier]

I realize my answer above may sound a bit mysterious ;-) so let me explain a bit more.
I don't think fno-builtin is desirable for TAs because, although TAs are supposed to use the GP API i.e., TEE_Malloc() rather than malloc() etc., we do provide libutils which is a partial implementation of the standard C library, so any assumption that the compiler could do about the standard functions should be valid, hence no need to disable those assumptions with -fno-builtin. Unless I'm missing something, which is why I'm asking for an example of a problem that is fixed with -fno-builtin.

[prime-zeng]

For example, if you have the codeprintf("x") in the ta source, it will report undefined reference to putchar.

[jforissier]

Ah, I see. So, builtins may generate calls to other standard functions that we may not have in our own libc (libutils). It makes sense, indeed.

Then I think what we need is -ffreestanding (which implies -fno-builtin). Can you test it please?

[prime-zeng]

I just tried and it works, can you help to add it to the default cflags for TAs.

[jforissier]

#1723

Thanks.

[prime-zeng]

#1754 resolve this problem, close it