• d-bugmail puremagic.com Jan 29 2010
• d-bugmail puremagic.com Jan 30 2010
• d-bugmail puremagic.com Jan 30 2010

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=3753

           Summary: ICE eh.c 49:  Related to exception handling and
                    alloca.
           Product: D
           Version: 2.039
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Keywords: ice-on-valid-code
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: dsimcha yahoo.com


--- Comment #0 from David Simcha <dsimcha yahoo.com> 2010-01-29 15:04:57 PST ---
I can't seem to reduce this one to a small test case, but I think this comment
from where the assert fires at least gives a hint that it involves some
combination of exceptions and alloca:

    // BUG: alloca() changes the stack size, which is not reflected
    // in the fixed eh tables.
    assert(!usedalloca);

Also, in the (too large to post to Bugzilla) program that this issue occurred
in, removing the alloca() calls and replacing them with GC.malloc() fixed the
problem.

This assert is in a #if TARGET_LINUX || TARGET_OSX || TARGET_FREEBSD ||
TARGET_SOLARIS statement, so I guess it only happens on those OS's.  The code
that triggers it definitely works on Windows.

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d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=3753


Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au


--- Comment #1 from Don <clugdbug yahoo.com.au> 2010-01-30 00:53:46 PST ---
(In reply to comment #0)
 I can't seem to reduce this one to a small test case, but I think this comment
 from where the assert fires at least gives a hint that it involves some
 combination of exceptions and alloca:
 
     // BUG: alloca() changes the stack size, which is not reflected
     // in the fixed eh tables.
     assert(!usedalloca);
 
 Also, in the (too large to post to Bugzilla) program that this issue occurred
 in, removing the alloca() calls and replacing them with GC.malloc() fixed the
 problem.


Are you sure you can't cut it down? Without a test case, the chance of it ever
getting fixed is pretty remote (basically, you have to wait until someone else
hits the same bug and files a test case). Even a huge test case would help.

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http://d.puremagic.com/issues/show_bug.cgi?id=3753



--- Comment #2 from David Simcha <dsimcha yahoo.com> 2010-01-30 06:48:29 PST ---
import core.stdc.stdlib;

void main(string[] args) {
    try { doNothing(); } catch {}
    void* foo = alloca(args.length);
}

void doNothing() {}

I've had some more time to fiddle with this and more insight into what causes
it, so I've managed to get a reduced test case working.  It seems like you need
to do both of the following in the same function:

1.  Use exception handling either explicitly or implicitly.  This can include
try-catch, try-finally, scope(exit), and struct destructors.

2.  Use alloca, but **the number of bytes must not be a compile-time
constant**.  This is what was messing me up before.  If you replace:

void* foo = alloca(args.length);

with:

void* foo = alloca(8);

then this bug will not be triggered.

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