Bug 227723
| Summary: | clang 6.0 breaks php56/opcache: Broken after clang 6.0 import (on CURRENT) | ||||||
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| Product: | Ports & Packages | Reporter: | lampa | ||||
| Component: | Individual Port(s) | Assignee: | Florian Smeets <flo> | ||||
| Status: | Closed FIXED | ||||||
| Severity: | Affects Only Me | CC: | clukas, devnexen, dpetrov67, flo, iron.udjin, toolchain | ||||
| Priority: | --- | Keywords: | regression | ||||
| Version: | Latest | Flags: | koobs:
merge-quarterly+
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| Hardware: | amd64 | ||||||
| OS: | Any | ||||||
| Attachments: |
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Description
lampa
2018-04-23 16:30:57 UTC
Created attachment 192772 [details]
Patch created by dim@
I reported this to dim@ when clang 6 was merged to head. He created the patch I attached. It didn't work in my case, I'm still using USE_GCC in my lang/php56 port. I haven't had the time to dig further. Maybe you can try the patch. Patch seems to be ok. I've only changed installed header files in /usr/local/include/php/Zend, recompiled/reinstalled opcache, restarted apache and it runs.
I've reduced problem to:
#include <stdio.h>
#include <stdlib.h>
#define EX_TMP_VAR(ex, n) ((temp_variable*)(((char*)(ex)) + ((int)(n))))
#define EX_TMP_VAR_NUM(ex, n) (EX_TMP_VAR(ex, 0) - (1 + (n)))
#define VAR_NUM(v) ((unsigned int)(EX_TMP_VAR_NUM(0, 0) - EX_TMP_VAR(0, v)))
typedef struct TV {
long tmp;
char tmp3[30];
} temp_variable;
int num;
int main()
{
printf("%x\n", VAR_NUM(-100));
return 0;
}
cc -O2 t.c
f999999c
clang50 -O2 t.c
1
gcc -O2 t.c
1
test case was for constant, which was optimized to immediate, here is another with variable:
#include <stdio.h>
#include <stdlib.h>
#define EX_TMP_VAR(ex, n) ((temp_variable*)(((char*)(ex)) + ((int)(n))))
#define EX_TMP_VAR_NUM(ex, n) (EX_TMP_VAR(ex, 0) - (1 + (n)))
#define VAR_NUM(v) ((unsigned int)(EX_TMP_VAR_NUM(0, 0) - EX_TMP_VAR(0, v)))
typedef struct TV {
long tmp;
char tmp3[30];
} temp_variable;
int num = -1000;
int main()
{
printf("%x\n", VAR_NUM(num));
return 0;
}
clang50 result is 18
clang60 result is 60000018
The only difference in generated code (clang50 first, clang60 second):
< movslq num(%rip), %rax
---
> movl num(%rip), %eax
movq $-40, %rcx
subq %rax, %rcx
shrq $3, %rcx
It looks like num is not sign extended before pointer arithmetic.
Over to maintainer. The patch works for the OP, I think in that case it should be committed to the port. I'll have to figure our why it didn't work for me, I probably applied it to the wrong poudriere ports tree. After some bisecting, it turns out this behavior changed due to the following upstream commit: https://reviews.llvm.org/rL313784 ("Remove offset size check in nullptr arithmetic handling") and https://reviews.llvm.org/rL313666 ("Teach clang to tolerate the 'p = nullptr + n' idiom used by glibc"). See also https://reviews.llvm.org/D37042. What PHP5 is doing is, strictly speaking, undefined behavior, as adding numbers to null pointers is normally not allowed. In the upstream commit, Andrew Kaylor has apparently tried to make this work, at least partially, for a few specific cases used in glibc. PHP7 and later use a completely different way of storing these variable/number hybrids, which is not affected by this, as it apparently avoids any null pointer arithmetic. I'll see if I can get some feedback from Andrew on this. That's true, if base nullptr is changed to any temp_variable* in VAR_NUM(), then generated code is identical and index is correctly sign extended. So this probably will be not fixed in clang and patch for php56 is more appropriate. After I manually applied this patch to php56-5.6.36 on 11.2-PRERELEASE r333394 it fixed the problem with opcache. Please commit this patch. A commit references this bug: Author: flo Date: Mon May 14 14:24:14 UTC 2018 New revision: 469895 URL: https://svnweb.freebsd.org/changeset/ports/469895 Log: Prevent php 5.6 (opcache) from segfaulting when compiled with clang 6.0 PR: 227723 Submitted by: dim Reported by: flo, lampa@fit.vutbr.cz Approved by: maintainer timeout MFH: 2018Q2 Changes: head/lang/php56/Makefile head/lang/php56/files/patch-Zend_zend__compile.h head/lang/php56/files/patch-Zend_zend__execute.h Patch was committed to the tree. A commit references this bug: Author: flo Date: Thu May 24 19:53:43 UTC 2018 New revision: 470806 URL: https://svnweb.freebsd.org/changeset/ports/470806 Log: MFH: r469895 Prevent php 5.6 (opcache) from segfaulting when compiled with clang 6.0 PR: 227723 Submitted by: dim Reported by: flo, lampa@fit.vutbr.cz Approved by: maintainer timeout Approved by: ports-secteam (riggs) Changes: _U branches/2018Q2/ branches/2018Q2/lang/php56/Makefile branches/2018Q2/lang/php56/files/patch-Zend_zend__compile.h branches/2018Q2/lang/php56/files/patch-Zend_zend__execute.h Assign to committer that resolved. Track merge to quarterly. |
