https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256
Bug ID: 83256
Summary: inconsistent _Pragma behavior in multi-line macros
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
Assignee: unassigned at gcc dot gnu.org
Reporter: arnd at linaro dot org
Target Milestone: ---
Created attachment 42777
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42777&action=edit
test case using _Pragma(GCC diagnostic push/pop)
I tried using _Pragma("GCC diagnostic push") and _Pragma("GCC diagnostic pop")
inside of a multi-line macro to turn a particular warning off inside code in
that macro. This worked in some cases but not others. From what I can tell, the
differences are:
- If I first preprocess the file with "gcc -E", and then compile the
preprocessed source, it works as expected.
- In case of the "-Wattribute-alias" warning (added in gcc-8), I get the
expected behavior only if I declare a structure before the _Pragma("GCC
diagnostic pop"); removing the 'struct s;' line from the attached example leads
to a warning for the incompatible alias.
- With the -Wuninitialized warning, I could find no way to disabled it just
inside of the macro expansion
The same thing seems to happen with multi-line statements that I join with '\'
line ends even without macros, but of course there is little use in that. I did
not try what happens with other. Support for _Pragma("GCC diagnostic ...") was
first added in gcc-4.2. This did not yet support push/pop, but the behavior of
multi-line macros was already the same as with gcc-8: preprocessing the file
makes it work as expected, but the integrated preprocessor seems to evaluate
the _Pragma() early.
