http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56240
Bug #: 56240
Summary: -fopenmp and -pthread behave inconsistently with
respect to -nostdlib
Classification: Unclassified
Product: gcc
Version: 4.4.5
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: y...@shurup.com
Hello,
As reported in #25460, if gcc is passed -nostdlib and -pthread options, the
libraries implied by -pthread are not added. It was decided that this is the
correct behavior and hence the bug was closed.
Now, if gcc is passed -nostdlib and -fopenmp, the libraries implied by -fopenmp
(and -pthread) are in fact added to the executable. The same test case as in
#25460 can be used to verify this (you have to use libtool 2.4.2+, however,
because earlier versions were filtering out OpenMP flags).
This behavior seems to be inconsistent to me.
In order to make it consistent, either the decision in #25460 can be
reconsidered and gcc can be made to adhere to -pthread even if -nostdlib is
specified, or the effect of -fopenmp can be changed in a way that gcc will not
add -lgomp and libraries implied by -pthread anymore.
I think that the first option is better, because the current behavior of
-fopenmp seems to make total sense to me, and, as a nice side effect, changing
the behavior of -pthread to match -fopenmp will "unbreak" libtool linking of
C++ programs that use threads.
The reasons why libtool uses -nostdlib / adds stubs directly and whether it
should do it or not can be debated, but they are outside the scope of this
report.
Thank you for your time,
--Yury.
