[Bug sanitizer/104718] New: Leak reported for elided static variable

[dlong at cadence dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104718

            Bug ID: 104718
           Summary: Leak reported for elided static variable
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dlong at cadence dot com
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at gcc dot gnu.org
  Target Milestone: ---

Created attachment 52523
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52523&action=edit
test case showing incorrect leak report

This is a case where g++ is able to detect that a section of code is
not used, and as a result it seems to be more-or-less eliding a
static variable that references some dynamically allocated storage.

It seems that this is confusing the leak sanitizer, which reports
the storage for that variable as leaked.

Normally, static variables which reference dynamically allocated
memory at program exit are not shown as leaks.

If you compile the attached test with:
g++-9.3.0 -std=c++17 -O2 -fsanitize=address -DUSE2=true lsantest.cc -o lsantest
so that the mutex mut2 is not elided and then run ./lsantest, the
program exits cleanly and reports no leaks.

If you compile it with:
g++-9.3.0 -std=c++17 -O2 -fsanitize=address -DUSE2=false lsantest.cc -o
lsantest
so that mut2 can be elided and then run ./lsantest, the sanitizer
will report a leak at exit.

mut1 is never elided and never reported as a leak.

mut2 will not be reported as a leak if use2 is just static bool instead
of static bool const.  Nor will it be reported as a leak if mut2 is
not declared static.