https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113401
Bug ID: 113401
Summary: Memory (resource) leak in -ftrampoline-impl=heap
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: fw at gcc dot gnu.org
Target Milestone: ---
Target: x86_64-*, aarch64-*
Consider this test program:
#include <err.h>
#include <errno.h>
#include <pthread.h>
static void *volatile compiler_barrier;
void *
thread_routine (void *ignore)
{
int local_variable;
auto int *local_function (void)
{
return &local_variable;
}
compiler_barrier = local_function;
return NULL;
}
int
main (void)
{
for (int i = 0; i < 10000; ++i)
{
pthread_t thread;
int ret = pthread_create (&thread, NULL, thread_routine, NULL);
if (ret != 0)
{
errno = ret;
err (1, "pthread_create");
}
ret = pthread_join (thread, NULL);
if (ret != 0)
{
errno = ret;
err (1, "pthread_join");
}
}
}
With -ftrampoline-impl=stack, I get:
$ \time ./a.out
0.01user 0.16system 0:00.18elapsed 102%CPU (0avgtext+0avgdata 3008maxresident)k
0inputs+0outputs (0major+68minor)pagefaults 0swaps
With -ftrampoline-impl=heap:
$ \time ./a.out
0.03user 0.17system 0:00.20elapsed 101%CPU (0avgtext+0avgdata
41796maxresident)k
0inputs+0outputs (0major+10148minor)pagefaults 0swaps
The reason for the maxresident change is that __builtin_nested_func_ptr_created
and __builtin_nested_func_ptr_deleted cache the last trampoline page even if it
is completely unused. This is required for performance reasons. The fix is to
register a TLS destructor to deallocate that page, too. On glibc, that also
fixes another memory leak for -fno-exceptions compilations (the default for C)
if pthread_exit is called with an active trampoline.
