How to suppress specific warnings in g++

Question

I want to suppress specific warnings from g++. I'm aware of the -Wno-XXX flag, but I'm looking for something more specific. I want some of the warnings in -Weffc++, but not all of them. Something like what you can do with lint - disable specific messages.

Is there a built in way in gcc to do this? Do I have to write a wrapper script?

See [this answer](https://stackoverflow.com/questions/3378560/how-to-disable-gcc-warnings-for-a-few-lines-of-code/26003732#26003732) if you want to disable the warnings for `n` lines of code. — Keith Morgan, Oct 06 '16 at 10:31
In case you are wiliiing to add it to the source code file(s) you can do the following as described here (and probably in other answers as well): https://codeyarns.com/2014/03/11/how-to-selectively-ignore-a-gcc-warning/ — Guy Avraham, Jul 18 '18 at 12:39

Luc Touraille · Accepted Answer · 2021-07-15T08:56:05.160

25

~~Unfortunately, this feature isn't provided by g++.~~ In VC++, you could use #pragma warning to disable some specific warnings. In gcc, the closest you can have is diagnostic pragmas, which let you enable/disable certain types of diagnostics for certain files or projects.

Edit: GCC supports pushing/popping warnings since 4.6.4 (see changelog)

edited Jul 15 '21 at 08:56

answered Jan 28 '09 at 12:55

Luc Touraille

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This is not correct, you can use the diagnostic pragma just around one line of code by pushing/popping the state and then tweaking the diagnostic within that push/pop area. – Alexis Wilke Jul 08 '21 at 20:05
1

@AlexisWilke Indeed, this was added in gcc a few years after my answer, let me update it! – Luc Touraille Jul 15 '21 at 08:51

score 13 · Answer 2 · edited Jul 08 '21 at 20:07

13

For some warnings, there is a command line switch to disable them. In order to know which switch to use, pass -fdiagnostics-show-option to gcc.

edited Jul 08 '21 at 20:07

Alexis Wilke

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answered Jan 28 '09 at 13:00

JesperE

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The command line option to get the name of the warning is useful. – Troy Daniels Dec 24 '14 at 01:22

score 3 · Answer 3 · answered Jan 28 '09 at 15:26

3

You could just use grep -v on the output.

Depending on the warning you wish to disable, you can sometimes correct in code. E.g.:

int main()
{
  int i;
}

Generates: foo.cc:4: warning: unused variable 'i'

Whereas this does not:

#define MARKUSED(X)  ((void)(&(X)))

int main()
{
  int i;
  MARKUSED(i);
}

answered Jan 28 '09 at 15:26

Mr.Ree

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GCC also has the keyword __extension__ wish will suppress warnings from the next statement. – Gilad Naor Jan 29 '09 at 08:13
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@GiladNaor Surround a section of code, e.g. `#pragma GCC diagnostic ignored "-Wfloat-equal"` and `#pragma GCC diagnostic pop` – Evgeni Sergeev Dec 25 '13 at 11:40
The op is asking for generic solution, not limited to this unused variable warning. – FaceBro Jan 05 '21 at 03:16

score 1 · Answer 4 · edited Jul 08 '21 at 20:06

1

pipe standard error to a filter that removes things you don't want to see. For example, this is my make file:

main.o:  main.cpp
    g++ -c -Wall main.cpp 2>&1 | grep -v Wunused-variable

edited Jul 08 '21 at 20:06

Alexis Wilke

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answered Mar 09 '13 at 23:03

Boris Z

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It seems to be more complex as a warning may fit multiple lines (say, when it contains code snippets). – AndreyS Scherbakov Jan 27 '18 at 00:52
Also if you use `-Werror`, hiding the warning is not that useful (to not say, it's not going to help you one bit). – Alexis Wilke Jul 08 '21 at 20:06

score 0 · Answer 5 · answered May 18 '23 at 20:53

0

When my colleagues are trying to prevent me from writing concise code, they use g++ command-line option

-Werror-parenthesis

And I disable this error in my code:

#pragma GCC diagnostic ignored "-Wparentheses"

answered May 18 '23 at 20:53

Frank Puck

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How to suppress specific warnings in g++

5 Answers5

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