[llvm-bugs] [Bug 44319] New: warnings promoted to error via pragma can not be demoted to warning via pragma

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44319

            Bug ID: 44319
           Summary: warnings promoted to error via pragma can not be
                    demoted to warning via pragma
           Product: clang
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: oliverhorn at gmx.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

Hello,

In the following piece of code Clang throws an error for the unused variable
even though it should only be a warning.

void func()
{
#pragma clang diagnostic error "-Wunused-variable"
#pragma clang diagnostic warning "-Wunused-variable"
    int a = 0;
}

The above example of course does not make much sense, but the warning option
could have been set to error in an included file or in the same file somewhere
earlier.

According to a test within godbolt.org this broke with Clang 3.1 (it is a
warning on Clang 3.0).

A workaround is to demote the warning flag to ignored and then promote to
warning again.

void func()
{
#pragma clang diagnostic error "-Wunused-variable"
#pragma clang diagnostic ignored "-Wunused-variable"
#pragma clang diagnostic warning "-Wunused-variable"
    int a = 0;
}

Compiling the following code with -Wunused-variable -Werror as command line
options works:

void func()
{
#pragma clang diagnostic warning "-Wunused-variable"
    int a = 0;
}

In GCC it works without the ignore as expected.

void func()
{
#pragma GCC diagnostic error "-Wunused-variable"
#pragma GCC diagnostic warning "-Wunused-variable"
    int a = 0;
}

Kind regards,
Oliver

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