https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63745
Bug ID: 63745
Summary: [4.9/5 Regression] mythtv build failure due to
aggressive speculative devirtualization
Product: gcc
Version: 4.9.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: trippels at gcc dot gnu.org
CC: hubicka at gcc dot gnu.org
With the attached unreduced testcase I get:
markus@x4 /tmp % g++ -flto -O2 foo.ii 2>&1 | grep
"VideoBuffers::StartDisplayingFrame"
markus@x4 /tmp % g++ -fno-devirtualize-speculatively -O2 foo.ii 2>&1 | grep
"VideoBuffers::StartDisplayingFrame"
markus@x4 /tmp % g++ -O2 foo.ii 2>&1 | grep
"VideoBuffers::StartDisplayingFrame"
/tmp/ccEenHoO.o:main.cpp:function VideoOutput::StartDisplayingFrame(): error:
undefined reference to 'VideoBuffers::StartDisplayingFrame()'
/tmp/ccEenHoO.o:main.cpp:function VideoPerformanceTest::Test(): error:
undefined reference to 'VideoBuffers::StartDisplayingFrame()'
Creduce came up with the following (invalid) testcase:
% cat main.ii
struct VideoBuffers
{
void StartDisplayingFrame ();
};
struct B
{
VideoBuffers vbuffers;
virtual void
StartDisplay ()
{
vbuffers.StartDisplayingFrame ();
}
};
struct VideoPerformanceTest
{
B *Test_vo;
void
Test ()
{
while (1)
Test_vo->StartDisplay ();
}
};
% g++ -fno-devirtualize-speculatively -O2 -Wl,--no-undefined main.ii
% g++ -flto -O2 -Wl,--no-undefined main.ii
% g++ -O2 -Wl,--no-undefined main.ii
/tmp/ccTlyhda.o:main.ii:function B::StartDisplay(): error: undefined reference
to 'VideoBuffers::StartDisplayingFrame()'
/tmp/ccTlyhda.o:main.ii:function main: error: undefined reference to
'VideoBuffers::StartDisplayingFrame()'
