CODEWITHSUNDEEP
cgccpragma
Aage Torleif
Aage Torleif

Reputation: 2013

How to ignore "useless storage class" with gcc using -Werror?

I compile my project with -Werror to make sure all of my code is without recognizable warnings. However my current project has a third-party dependency that has an issue in it which causes a warning - and that warning fails my build because of the -Werror flag.

I want to use the -Werror flag and I don't want to correct the third-party package. Is there a way to ignore this warning? 

package.h:126:1: error: useless storage class specifier in empty declaration [-Werror]
 };

The line of code that generates the error is a struct definition with a "dangling" typedef.

typedef struct my_data_obj {
  char* data;
  uint32_t data_size;
};

This is obviously a mistake - but I can't find any pragma or any such mechanic to ignore the warning generated from that header file. Any ideas?

EDIT: SOLUTION

Though I'm accepting Florian Weimer's answer because it answers the question most closely it's not the actual fix I settled with. I'll describe that bellow. By including the headers as system headers I did exactly what I wanted to do - suppress the error without having to fix the package.

What I finally did was create a patch file and simply apply that patch each time the project is built.

vim package.h
# fix the file
git add package.h
git diff --cached > package.h.patch

# on build time
git apply package.h.patch

Upvotes: 2

Views: 576

Answers (2)

Florian Weimer
Florian Weimer

Reputation: 33719

I assume that you want to include package.h from files where you want to enable -Werror.

GCC does not have a separate flag to control this warning, otherwise the compiler would have printed it. With the separate flag, you could have used #pragma GCC diagnostics ignore, as indicated in the other answers, possibly with a wrapper header file.

However, you could put the header file into a separate directory, and instead of using -I to add it to the include path, use -isystem. As a result, the header file is treated as a system header, and unless you also compile with -Wsystem-headers, warnings in system headers are suppressed.

Upvotes: 3

Some programmer dude
Some programmer dude

Reputation: 409196

All warnings and errors have specific names, and can be enabled or disabled on a per-warning/-error basis.

For example lets say I have an unused variable and enabled warnings about it, then I will get a message similar to

/some/path/main.cpp:18:9: warning: unused variable ‘i’ [-Wunused-variable]

That last part of the message, the one inside the square brackets, is the name of the specific warning.

With this name you can then disable warnings using the -Wno-<name of warning> option. In the case of the above warning it's disabled with -Wno-unused-variable.

Your use-case is a little different in that you want to disable a warning turned into an error. This is very similar to the above, but the general form of the option is -Wno-error=<name of warning or error>. In our example case it's -Wno-error=unused-variable.

All of this is of course in the GCC documentation, more specifically in the warning options documentation.

So what you have to do is figure out the name of the warning, so you can use it for the -Wno-error= option.

Upvotes: -1

Related Questions