The gcc 4.9 release notes warn about this optimization: https://gcc.gnu.org/gcc-4.9/porting_to.html
I'm surprised that this change hasn't caused more trouble for us. At Tue, 12 Aug 2014 08:39:01 +0100, Matthew Flatt wrote: > Apparently, when gcc 4.9.1 sees > > memcpy(x, y, n); > if (y) > .... > > then it believes `y` can be assumed to be NULL --- even if `n` turns > out to be zero --- and so the conditional can be optimized away. > > I'm surprised by that rule, but it's easy enough to move the test > before the memcpy(). > > At Tue, 12 Aug 2014 02:00:04 -0400, Asumu Takikawa wrote: > > On 2014-08-12 06:06:51 +0100, Matthew Flatt wrote: > > > What platform are you using? > > > > > > I imagine that running `./racketcgc` within the "racket" subdirectory > > > of your build directory will similarly crash. Can you get any > > > information from running `gdb racketcgc`? > > > > This is on Linux. Running the built executable immediately produces a > segfault. > > > > Here's a backtrace from gdb: > > (gdb) bt > > #0 0x00000000005e78db in free_managed (s=s@entry=0x0) at > > ../../../racket/sgc/sgc.c:1535 > > #1 0x00000000005e7f63 in GC_add_roots (start=start@entry=0x881b70 > > <collects_path>, end=end@entry=0x881b79 <run_cmd+1>) at > > ../../../racket/sgc/sgc.c:1657 > > #2 0x0000000000576f9a in scheme_register_static (ptr=ptr@entry=0x881b70 > > <collects_path>, size=size@entry=8) at ../../../racket/src/salloc.c:720 > > #3 0x000000000045b87f in scheme_set_collects_path > (p=p@entry=0x7ffff7f701a0) > > at ../../../racket/src/file.c:6841 > > #4 0x0000000000436673 in run_from_cmd_line (mk_basic_env=<optimized > > out>, > > cont_run=0x435a10 <cont_run>, _argv=<optimized out>, argc=0) at > > ../../racket/cmdline.inc:1444 > > #5 main_after_stack (data=data@entry=0x7fffffffdc30) at > > ../../racket/main.c:450 > > #6 0x000000000057694d in do_main_stack_setup (data=0x7fffffffdc30, > > _main=0x435a80 <main_after_stack>, no_auto_statics=1) at > > ../../../racket/src/salloc.c:198 > > #7 scheme_main_stack_setup (no_auto_statics=no_auto_statics@entry=1, > > _main=_main@entry=0x435a80 <main_after_stack>, > > data=data@entry=0x7fffffffdc30) > > at ../../../racket/src/salloc.c:310 > > #8 0x00000000004346ee in main_after_dlls (argv=<optimized out>, > > argc=<optimized out>) at ../../racket/main.c:381 > > #9 main (argc=<optimized out>, argv=<optimized out>) at > > ../../racket/main.c:341 > > > > Cheers, > > Asumu > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev _________________________ Racket Developers list: http://lists.racket-lang.org/dev
