My initial report was garbled.

What I mean is that a protection violation occurs in mdb.c when I add a 13'th item to a multiset and I compile with one of the mentioned compilers and with -fPIC -O3. The code works fine when compiled with older GCC compilers or with -O0 or with -fno-strict-aliasing.

Given what I read at https://gcc.gnu.org/bugs/ under section "Casting does not work as expected when optimization is turned on", I suspect the problem is simply that a pointer variable is not following the ISO C aliasing rules and breaks with the new, more aggressive compiler optimization.

Here is the part that fails:

for (i=0; i<NUMKEYS(fp); i++) mp->mp_ptrs[i] = fp->mp_ptrs[i] + offset;

If this turns out to not be straightforward, I can try building a small test program to reproduce the problem.

On 04/03/2016 09:44 AM, Howard Chu wrote:

bdallen@nps.edu wrote:

...

Full_Name: Bruce Allen Version: 2.4.44 OS: Fedora 23 URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (205.155.65.226)

LMDB v0.9.18 crashes with segmentation fault in mdb.c line 6590 when compiled using these compilers:

• gcc (GCC) 5.3.1 20151207 (Red Hat 5.3.1-2)
• x86_64-w64-mingw32-gcc (GCC) 5.2.0 20150716 (Fedora MinGW

5.2.0-1.fc23)

The crash happens afterrititing the 12'th item (with the same key but different value using flags MDB_NODUPDATA and MDB_DUPSORT).

Your message appears garbled here. Please send a test case with steps to reproduce.

...

The problem goes away when compiling mdb.c with the -fno-strict-aliasing flag.