CODEWITHSUNDEEP
cclang
thinkerou
thinkerou

Reputation: 1877

How can I ignore an error when using GCC compile option '-Werror'?

I have the following test code, file test.c:

#include <stdio.h>

int *func()
{
    int i = 123;
    return &i;
}

int main()
{
    printf("%d\n", *func());
}

If I use the command to compile it that is OK,

gcc test.c -o test

It will have the following warning information:

warning: address of stack memory associated with local variable 'i'
  returned [-Wreturn-stack-address]
return &i;
        ^
1 warning generated.

But it can output the result: 123

If I use the command:

gcc -Werror test.c -o test

It will have the following error information:

error: address of stack memory associated with local variable 'i'
  returned [-Werror,-Wreturn-stack-address]
return &i;
        ^
1 error generated.

Now I want to use the -Werror option, but I also want to ignore the address of stack memory associated with local variable 'i' warning. What should I do?

Upvotes: 5

Views: 15282

Answers (2)

Clint Chelak
Clint Chelak

Reputation: 242

According to the gcc documentation about -Werror, you can "negate -Werror for specific warnings" with -Wno-error=. In our case, we can ignore -Wreturn-stack-address -Wno-error=return-stack-address as follows:

gcc -Werror -Wno-error=return-stack-address test.c -o test

As already stated another answer here, you can disable most warnings by appending no- to the warning name. In the documentation linked above:

Each of these specific warning options also has a negative form beginning -Wno- to turn off warnings; for example, -Wno-implicit."

I recognize that the example given is this question is just an example. Places where I've needed this are from compiling external libraries that I cannot edit, due to licensing or other reasons. Often, I can put in a ticket to remove the warning, but in the meantime, I assess the risk and choose to silence the warning until an update comes.

Upvotes: 0

ShadowRanger
ShadowRanger

Reputation: 155438

Most gcc warnings can be disabled by prefixing the name of the warning with no-, e.g. -Wno-return-stack-address.

That said, this is not something you want to ignore; returning pointers to stack variables is undefined behavior, and while it has semi-predictable results on most compilers, it's incredibly fragile; any function call at all, implicit or explicit, could stomp on the value that pointer is referencing.

Upvotes: 12

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