On 17/06/2014 19:11, Jon TURNEY wrote:
I think I have found a problem when building programs using the latest
mesa library, where abort is being called during exit()
This seems to be x86 specific, and looks like it is somehow related to
having a C++ library dynamically loaded by a C program.
I think I have reduced it to the following test case:
So, this seems to be related to this patch [1], to fix a different abort
during __gcc_deregister_frame()
[1] https://sourceware.org/ml/cygwin/2013-07/msg00528.html
Since this code is baked into libgcc itself, that patch has the
side-effect of making libgcc pin itself in memory.
I can't really tell from what's written there if that was deliberate or
not, but it seems that it introduces a different problem when the
executable doesn't have a dependency on libgcc.
test.c:
#include <assert.h>
#include <dlfcn.h>
int main()
{
void *h = dlopen("dllib.dll", 0);
assert(h);
dlclose(h);
The problem can be worked around by adding code to force libgcc to get
unloaded here, which seems to support this theory, e.g.
+#define LIBGCC_SONAME "cyggcc_s-1.dll"
+ HANDLE hmod_libgcc = GetModuleHandle(LIBGCC_SONAME);
+ FreeLibrary(hmod_libgcc);
}
Attached is a patch which modifies __gcc_register_frame() to avoid it
pinning itself in memory.
Alternatively, as one of the emails in the linked thread says [2], the
assert in __deregister_frame_info_bases() itself could be removed.
[2] http://www.mail-archive.com/gcc@gcc.gnu.org/msg68286.html
--- cygming-crtbegin.c.bak 2014-07-03 16:41:43.116600000 +0100
+++ cygming-crtbegin.c 2014-07-03 18:39:07.436800000 +0100
@@ -99,8 +99,21 @@
if (h)
{
- /* Increasing the load-count of LIBGCC_SONAME DLL. */
- hmod_libgcc = LoadLibrary (LIBGCC_SONAME);
+ /*
+ Increase the load-count of the LIBGCC_SONAME DLL by one, so that it
remains
+ loaded as long as this module is, so that __gcc_deregister_frame()
will call
+ __deregister_frame_info() in that DLL, to match the
register_frame_info()
+ we do now.
+
+ Unless this *is* LIBGCC_SONAME DLL, where increasing our own
load-count would
+ make us self-pinning.
+ */
+ HMODULE hmod_this = 0;
+ GetModuleHandleEx (GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+ (LPCTSTR)__gcc_register_frame, &hmod_this);
+ if (hmod_this != h)
+ hmod_libgcc = LoadLibrary (LIBGCC_SONAME);
+
register_frame_fn = (void (*) (const void *, struct object *))
GetProcAddress (h, "__register_frame_info");
}
--
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