https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70722
Bug ID: 70722
Summary: include_next in cmath skips user-defined wrapper
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: martin.thomson at gmail dot com
Target Milestone: ---
Firefox has a bunch of wrappers for system headers. I'm not 100% on the
reasoning, but most just play with visibility. For instance, the math.h
wrapper looks like:
#pragma GCC system_header
#pragma GCC visibility push(default)
#include_next <math.h>
#pragma GCC visibility pop
Firefox fails to link when built with libstdc++ 6.0.0 because it includes
<cmath> before it includes <math.h>. This leads to inclusion of <math.h> with
different visibility than is desired.
The version of cmath I have includes this:
#define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
#include_next <math.h>
#undef _GLIBCXX_INCLUDE_NEXT_C_HEADERS
Removing the "_next" causes the build to succeed.
You can see my flailings regarding this issue here:
https://bugzilla.mozilla.org/show_bug.cgi?id=1264534
