Bug 14630 – Std.algorithm splitter segfault on large file with mmfile, seems GC related.

Created attachment 1524 Code to generate a large file that will segfault std.algorithm.splitter. I discovered that std.algorithm's splitter function segfaults when called over casted memory mapped filed. Interestingly I found this when reenabling the GC on an application we've been running for a long time with GC.disable(). The bug does not occur with GC.disable, but with GC enabled it segfaults everytime. Linked is a test program that segfaults when run in a Ubuntu 12.04 VM on a mid-2014 MBR. Seems transient when compiled with -g flag. Seems to only segfault on large files. http://dpaste.dzfl.pl/96e898051fb2 Backtrace from core dump: #0 memchr () at ../sysdeps/x86_64/memchr.S:59 #1 0x000000000045dc0f in std.algorithm.searching.__T4findVAyaa6_61203d3d2062TAyaTaZ.find() () #2 0x000000000045db86 in std.algorithm.searching.__T4findVAyaa6_61203d3d2062TAyaTaZ.find() () #3 0x000000000045d051 in std.algorithm.iteration.__T8splitterVAyaa6_61203d3d2062TAyaTaZ.splitter() () #4 0x000000000045a622 in gen_map.file_to_map() () #5 0x000000000045a7b3 in D main () #6 0x0000000000463abb in rt.dmain2._d_run_main() () #7 0x0000000000463a0e in rt.dmain2._d_run_main() () #8 0x0000000000463a74 in rt.dmain2._d_run_main() () #9 0x0000000000463a0e in rt.dmain2._d_run_main() () #10 0x0000000000463988 in _d_run_main () #11 0x000000000045f38f in main ()

The problem is that MmFile is a class and the construct "cast(string)mapFile[]" doesn't prevent the object from being collected. Declaring the variable with scope scope mapFile = new MmFile(map_path); or simply using it after the loop foreach(line ; splitter(cast(string)mapFile[], '\n')) { ... } mapFile.length; makes the program succeed.