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Issue 7750 - while(true) loop with try/catch block causes segfault
Summary: while(true) loop with try/catch block causes segfault
Status: RESOLVED FIXED
Alias: None
Product: D
Classification: Unclassified
Component: dmd (show other issues)
Version: D2
Hardware: All Mac OS X
: P2 critical
Assignee: No Owner
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2012-03-21 21:56 UTC by Brian Palmer
Modified: 2012-04-24 18:58 UTC (History)
3 users (show)

See Also:


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Description Brian Palmer 2012-03-21 21:56:22 UTC
I ran into a segfault when using a try/catch block inside a while(true) loop when there are other statements after the try/catch block. I reduced it down to this consistent segfault:

import std.stdio;

void main() {
  while (true) {
    try {
      throw new Exception("ah");
    } catch (Exception e) {
    }
    writeln("remove this line and it won't segfault");
  }
}

This segfaults in the first iteration on DMD 2.058 on OS X 10.7.3. It segfaults with both -m32 and -m64. Stacktrace:

0   libdyld.dylib                 	0x00007fff8f3436cd misaligned_stack_error_entering_dyld_stub_binder + 0
1   ???                           	0x000000010f535030 0 + 4552085552
2   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f51f133 _Dmain + 103
3   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f52f8dd D2rt6dmain24mainUiPPaZi7runMainMFZv + 29
4   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f52f28d D2rt6dmain24mainUiPPaZi7tryExecMFMDFZvZv + 45
5   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f52f92f D2rt6dmain24mainUiPPaZi6runAllMFZv + 63
6   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f52f28d D2rt6dmain24mainUiPPaZi7tryExecMFMDFZvZv + 45
7   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f52f210 main + 232
8   bug1.d.DC445724916B27653F5E50703AE848DF	0x000000010f51f0c4 start + 52


Removing the writeln, or changing it to a non-infinite loop like int x;while(++x<3) will avoid the segfault, so it seems likely DMD is making a bad assumption about the loop related to it being infinite.
Comment 1 hsteoh 2012-03-27 21:09:58 UTC
I can't seem to reproduce this problem with the latest git dmd (2.059 candidate) on Linux AMD64. Could it be a Mac-specific problem?
Comment 2 Don 2012-03-27 23:33:22 UTC
(In reply to comment #1)
> I can't seem to reproduce this problem with the latest git dmd (2.059
> candidate) on Linux AMD64. Could it be a Mac-specific problem?

Looks like it, based on the first location in the backtrace:
misaligned_stack_error_entering_dyld_stub_binder

The stack isn't getting aligned properly before the call to writeln.
Comment 3 Don 2012-04-11 00:59:23 UTC
Probably related to bug 1115.
Comment 4 github-bugzilla 2012-04-24 18:56:32 UTC
Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/1fba8be9f381c01315d01d74b52ce616c5afc745
fix Issue 7750 - while(true) loop with try/catch block causes segfault
Comment 5 github-bugzilla 2012-04-24 18:56:46 UTC
Commit pushed to dmd-1.x at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/99c11c44985493a1e9974bad8510cf377cd208a5
fix Issue 7750 - while(true) loop with try/catch block causes segfault