digitalmars.D.bugs - [Issue 6215] New: ICE(el.c) DMD segfaults when built on system with XCode 4.2
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http://d.puremagic.com/issues/show_bug.cgi?id=6215
Summary: ICE(el.c) DMD segfaults when built on system with
XCode 4.2
Product: D
Version: D1 & D2
Platform: Other
OS/Version: Mac OS X
Status: NEW
Severity: blocker
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: robert octarineparrot.com
--- Comment #0 from Robert Clipsham <robert octarineparrot.com> 2011-06-26
14:28:18 BST ---
As of XCode 4.2 (maybe 4.1, I skipped it), Apple has made gcc a symlink for
llvm-gcc. When built using llvm-gcc, dmd sefaults in el.c:211:
void test(){}
void main(){}
$ dmd test.d
Segmentation fault
It fails in el.c:211.
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Jacob Carlborg <doob me.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |doob me.com
--- Comment #1 from Jacob Carlborg <doob me.com> 2011-06-26 08:34:11 PDT ---
GCC is a symlink for LLVM-GCC with XCode 4.1 as well.
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--- Comment #2 from Robert Clipsham <robert octarineparrot.com> 2011-06-26
19:33:46 BST ---
The following patch is a workaround, it seems something's going wrong with the
elem recycling system:
----
diff --git a/src/backend/el.c b/src/backend/el.c
index f5fa66d..9cc34fc 100644
--- a/src/backend/el.c
+++ b/src/backend/el.c
-195,6 +195,7 elem *el_calloc()
static elem ezero;
elcount++;
+#if 0
if (nextfree)
{ e = nextfree;
nextfree = e->E1;
-209,6 +210,9 elem *el_calloc()
eprm_cnt++;
#endif
*e = ezero; /* clear it */
+#else
+ e = (elem *)mem_fmalloc(sizeof(elem));
+#endif
#ifdef DEBUG
e->id = IDelem;
----
If you print e and *e, *e is NULL, hence the segfault when assigned to.
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Jun 26 2011
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Sean Kelly <sean invisibleduck.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |sean invisibleduck.org
--- Comment #3 from Sean Kelly <sean invisibleduck.org> 2011-08-11 16:16:23 PDT
---
The first problem is in el_calloc():
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: 13 at address: 0x00000000
0x0009fc2f in el_calloc () at el.c:189
189 *e = ezero; /* clear it */
(gdb) p e
$1 = (elem *) 0xa4e7bc
Current language: auto; currently c++
(gdb)
I can't explain why this isn't working, but it's easily fixed by replacing the
assignment with:
memset(e, 0, sizeof(elem));
That gets us to the next error:
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: 13 at address: 0x00000000
0x000aa08d in evalu8 (e=0xa50988) at evalu8.c:625
625 esave = *e;
(gdb) p e
$1 = (elem *) 0xa50988
Current language: auto; currently c++
(gdb)
Which is similarly fixed by replacing the assignment with:
memcpy(&esave, e, sizeof(elem));
These two changes are enough for LLVM-DMD to build druntime.
Given the two errors above, the problem seems to be with the default assignment
operator LLVM generates for the elem struct. It's a very weird problem though.
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Aug 11 2011
http://d.puremagic.com/issues/show_bug.cgi?id=6215
Brad Roberts <braddr puremagic.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |braddr puremagic.com
--- Comment #4 from Brad Roberts <braddr puremagic.com> 2011-08-11 16:41:20 PDT
---
Would you take that info and try the same sort of code in a standalone test
case? If struct assignment is indeed the problem, that's a pretty embarrassing
llvm bug, imho, and clearly should be reported to either llvm directly or apple
as the provider of that version of the compiler.
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klickverbot <code klickverbot.at> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |code klickverbot.at
--- Comment #5 from klickverbot <code klickverbot.at> 2011-08-12 02:25:33 PDT
---
(In reply to comment #3)
Given the two errors above, the problem seems to be with the default assignment
operator LLVM generates for the elem struct. It's a very weird problem though.
Note that at least the first error happens with both LLVM-GCC, which uses the
GCC frontend, and Clang.
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http://d.puremagic.com/issues/show_bug.cgi?id=6215 --- Comment #6 from klickverbot <code klickverbot.at> 2011-08-12 04:24:54 PDT --- The difference in the LLVM IR generated by Clang for the ezero change is only: - call void llvm.memcpy.p0i8.p0i8.i32(i8* %17, i8* getelementptr inbounds (%struct.elem* _ZZ9el_callocvE5ezero, i32 0, i32 0), i32 80, i32 16, i1 false) + call void llvm.memset.p0i8.i32(i8* %17, i8 0, i32 80, i32 1, i1 false) Note that the second last parameter to memcpy is the alignment (16 bit), but GDB says that »(int)e % 16« is 8. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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--- Comment #7 from klickverbot <code klickverbot.at> 2011-08-12 05:06:27 PDT
---
And indeed, __alignof__(*e) gives 16, patching the allocator to 16-byte align
everything is easy:
--- a/src/tk/mem.c
+++ b/src/tk/mem.c
-758,7 +758,7 void *mem_fmalloc(unsigned numbytes)
if (sizeof(size_t) == 2)
numbytes = (numbytes + 1) & ~1; /* word align */
else
- numbytes = (numbytes + 3) & ~3; /* dword align */
+ numbytes = (numbytes + 15) & ~15;
/* This ugly flow-of-control is so that the most common case
drops straight through.
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http://d.puremagic.com/issues/show_bug.cgi?id=6215 --- Comment #8 from klickverbot <code klickverbot.at> 2011-08-12 06:17:46 PDT --- A preliminary patch which only 16 byte aligns allocations when building with a LLVM backend is at: https://github.com/D-Programming-Language/dmd/pull/301. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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http://d.puremagic.com/issues/show_bug.cgi?id=6215 --- Comment #9 from Jacob Carlborg <doob me.com> 2011-08-12 06:24:59 PDT --- Is this specific to Mac OS X or is it like this with LLVM in general? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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http://d.puremagic.com/issues/show_bug.cgi?id=6215 --- Comment #10 from klickverbot <code klickverbot.at> 2011-08-12 06:53:35 PDT --- (In reply to comment #9)Is this specific to Mac OS X or is it like this with LLVM in general?Happens on my Linux x86_64 box too. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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http://d.puremagic.com/issues/show_bug.cgi?id=6215 --- Comment #11 from Sean Kelly <sean invisibleduck.org> 2011-08-12 09:08:45 PDT --- Awesome. I figured it was an alignment mistake for the copy, but ran out of time to investigate. What an embarrassing bug for LLVM. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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http://d.puremagic.com/issues/show_bug.cgi?id=6215 --- Comment #12 from klickverbot <code klickverbot.at> 2011-08-12 13:50:59 PDT --- (In reply to comment #11)Awesome. I figured it was an alignment mistake for the copy, but ran out of time to investigate. What an embarrassing bug for LLVM.Just for clarity, let me note that this is definitely _not_ a bug in LLVM, it just happens with two compilers using LLVM as their backend. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |bugzilla digitalmars.com
Resolution| |FIXED
--- Comment #13 from Walter Bright <bugzilla digitalmars.com> 2011-08-12
18:28:32 PDT ---
https://github.com/D-Programming-Language/dmd/commit/77838ef515fa69bf7f379d3ff6cff0b19b49577e
https://github.com/D-Programming-Language/dmd/commit/06d04bf519f7103ab5a39dff0f863979dbdc8bd2
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