[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531]
This should be marked FIXED as of 4.7.0 . Ramana -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
For the record, this bites QEMU compiled on Natty as well (and results in an immediate crash on startup). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531]
Author: jye2 Date: Mon Sep 19 08:13:02 2011 New Revision: 178955 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=178955 Log: 2011-09-19 Jiangning Liu Backport r175427 from mainline 2011-06-27 Richard Guenther PR tree-optimization/49169 * fold-const.c (get_pointer_modulus_and_residue): Don't rely on the alignment of function decls. 2011-09-19 Jiangning Liu Backport r175208 from mainline 2011-06-20 Ramana Radhakrishnan PR target/49385 * config/arm/thumb2.md (*thumb2_movhi_insn): Make sure atleast one of the operands is a register. 2011-09-19 Jiangning Liu Backport r174803 from mainline 2011-06-08 Julian Brown * config/arm/arm.c (arm_libcall_uses_aapcs_base): Use correct ABI for double-precision helper functions in hard-float mode if only single-precision arithmetic is supported in hardware. Modified: branches/ARM/embedded-4_6-branch/gcc/ChangeLog.arm branches/ARM/embedded-4_6-branch/gcc/config/arm/arm.c branches/ARM/embedded-4_6-branch/gcc/config/arm/thumb2.md branches/ARM/embedded-4_6-branch/gcc/fold-const.c -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
fixed in oneiric in gcc-4.5 ** Changed in: gcc-4.5 (Ubuntu Oneiric) Status: Triaged => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Branch linked: lp:debian/gnat-4.6 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc-linaro/4.6 Status: Fix Committed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc-linaro/4.5 Status: Fix Committed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Branch linked: lp:debian/gcc-4.6 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
This bug was fixed in the package gcc-4.6 - 4.6.1-4ubuntu1
---
gcc-4.6 (4.6.1-4ubuntu1) oneiric; urgency=low
* Merge with Debian.
gcc-4.6 (4.6.1-4) unstable; urgency=low
* Update to SVN 20110714 (r176280) from the gcc-4_6-branch.
- Fix PR tree-optimization/49094, PR target/39633, PR c++/49672,
PR fortran/49698, PR fortran/49690, PR fortran/49562, PR libfortran/49296,
PR target/49487, PR tree-optimization/49651, PR ada/48711.
[ Matthias Klose ]
* Build Go on alpha for gcc-snapshot builds.
* For multicore ARM, clear both caches, not just the dcache (proposed
patch by Andrew Haley).
* Fix for PR rtl-optimization/{48830,48808,48792}, taken from the trunk.
LP: #807573.
* Fix PR tree-optimization/49169, optimisations strip the Thumb/ARM mode bit
off function pointers (Richard Sandiford). LP: #721531.
[ Marcin Juszkiewicz ]
* Define DEB_TARGET_MULTIARCH macro.
* debian/rules2: Macro and configuration consolidation.
gcc-4.6 (4.6.1-3) unstable; urgency=medium
* Update to SVN 20110709 (r176108) from the gcc-4_6-branch.
- Fix PR target/49335, PR tree-optimization/49618, PR c++/49598,
PR fortran/49479, PR target/49621, PR target/46779, PR target/49660,
PR c/49644, PR debug/49522, PR debug/49522, PR middle-end/49640,
PR c++/48157, PR c/49644, PR fortran/48926.
- Apparently fixes a boost issue. Closes: #632938.
* Apply proposed patch for PR fortran/49690. Closes: #631204.
* README.Debian: New section 'Former and/or inactive maintainers'.
-- Matthias KloseThu, 14 Jul 2011 20:18:27 +0200
** Changed in: gcc-4.6 (Ubuntu Oneiric)
Status: New => Fix Released
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[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Also affects: gcc-4.6 (Ubuntu) Importance: Undecided Status: New ** Changed in: gcc-4.6 (Ubuntu Natty) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc Status: New => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Also affects: gcc-linaro/4.5 Importance: Medium Assignee: Richard Sandiford (rsandifo) Status: In Progress ** Also affects: gcc-linaro/4.6 Importance: Undecided Status: New ** Changed in: gcc-linaro/4.5 Status: In Progress => Fix Committed ** Changed in: gcc-linaro/4.6 Status: New => Fix Committed ** Changed in: gcc-linaro/4.6 Importance: Undecided => Medium ** Changed in: gcc-linaro/4.6 Assignee: (unassigned) => Richard Sandiford (rsandifo) ** Changed in: gcc-linaro/4.6 Milestone: None => 4.5-2011.07 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc-linaro Milestone: None => 4.6-2011.07 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc-linaro Status: Triaged => In Progress -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531]
Author: rsandifo Date: Mon Jun 27 09:33:06 2011 New Revision: 175427 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175427 Log: gcc/ 2011-07-24 Richard Guenther PR tree-optimization/49169 * fold-const.c (get_pointer_modulus_and_residue): Don't rely on the alignment of function decls. gcc/testsuite/ 2011-07-24 Michael Hope Richard Sandiford PR tree-optimization/49169 * gcc.dg/torture/pr49169.c: New test. Added: trunk/gcc/testsuite/gcc.dg/torture/pr49169.c Modified: trunk/gcc/ChangeLog trunk/gcc/fold-const.c trunk/gcc/testsuite/ChangeLog -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Branch linked: lp:~rsandifo/gcc-linaro/lp721531-4.5 ** Branch linked: lp:~rsandifo/gcc-linaro/lp721531-4.6 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc-linaro Assignee: (unassigned) => Richard Sandiford (rsandifo) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/721531/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531]
(In reply to comment #3) > Btw, we finally should introduce a target hook for this I think. Thanks for the patch in comment #2. How strongly do you feel about the hook though? In PR35705, it sounded like a lot of targets actually need an opt-out for functions, either because of ISA encoding (ARM, MIPS, SH) or because of function descriptors (IA-64, PA, PPC). I notice that ARM and mcore also have optimisation-dependent FUNCTION_BOUNDARYs. Arguably (very arguably) that's a bug, and they should be using align_functions instead. But if we make a deliberate decision to honour DECL_ALIGN on functions, then FUNCTION_BOUNDARY really will be an ABI property. I'm just worried that the combination of that and the need to identify exactly which targets should define the hook might be more hassle than the optimisation is worth. You said in that bug that masking function addresses isn't likely to be a common operation, and TBH, I still agree. Richard -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531]
Btw, we finally should introduce a target hook for this I think. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531]
There are several places in the compiler where we assume DECL_ALIGN
constraints the lower bits of the address of the DECL.
See several similar bugs in the past (PR47239 comes to my mind).
fold-const.c:get_pointer_modulus_and_residue looks suspicious to me here,
so you might want to try
Index: gcc/fold-const.c
===
--- gcc/fold-const.c(revision 174266)
+++ gcc/fold-const.c(working copy)
@@ -9219,7 +9219,8 @@ get_pointer_modulus_and_residue (tree ex
*residue = 0;
code = TREE_CODE (expr);
- if (code == ADDR_EXPR)
+ if (code == ADDR_EXPR
+ && TREE_CODE (TREE_OPERAND (expr, 0)) != FUNCTION_DECL)
{
unsigned int bitalign;
bitalign = get_object_alignment_1 (TREE_OPERAND (expr, 0), residue);
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[Bug 721531]
Try passing the function pointer through an opaque identity transform:
asm("" : "=r"(p) : "0"(main));
if ((uintptr_t)p & 1) /* do thumb case */
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[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
Launchpad has imported 1 comments from the remote bug at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49169.
If you reply to an imported comment from within Launchpad, your comment
will be sent to the remote bug automatically. Read more about
Launchpad's inter-bugtracker facilities at
https://help.launchpad.net/InterBugTracking.
On 2011-05-26T02:13:27+00:00 Michael Hope wrote:
ARM devices encode the instruction set mode in the LSB of the function
address. Functions are word aligned on ARM. If you try to test the LSB
of a function pointer then GCC assumes that the two least significant
bits are zero and optimises away the test.
This problem is seen in Mono and was originally reported at:
https://bugs.launchpad.net/ubuntu/+source/gcc-4.5/+bug/721531
A reduced test case is:
void main() {
void *p = main;
if ((int)p & 1) printf ("HIT!\n");
}
When compiled with -march=armv7-a -mthumb -O0 then the word 'HIT!' will
show. When compiled with -O2, the branch is not taken.
The problem does not occur in 4.4.5. It does occur in 4.5.2, 4.6.0, and
trunk r174044.
Reply at: https://bugs.launchpad.net/gcc/+bug/721531/comments/18
** Changed in: gcc
Status: Unknown => New
** Changed in: gcc
Importance: Unknown => Medium
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[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
I've logged this in GCC bugzilla. We'll get it fixed up there. ** Bug watch added: GCC Bugzilla #49169 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49169 ** Also affects: gcc via http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49169 Importance: Unknown Status: Unknown -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
This fault exists in all upstream versions from 4.5 onwards including recent trunk: michaelh@ursa2:~/linaro/bugs$ uname -a Linux ursa2 2.6.35.3-cbuild2+ #8 SMP Mon Apr 4 12:46:46 NZST 2011 armv7l GNU/Linux michaelh@ursa2:~/linaro/bugs$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:Ubuntu 10.10 Release:10.10 Codename: maverick michaelh@ursa2:~/linaro/bugs$ /tools/toolchains/gcc-4.4.5-armv7l-maverick-cbuild93-ursa2-cortexa8r1/bin/gcc -O2 align.c ; ./a.out HIT! michaelh@ursa2:~/linaro/bugs$ /tools/toolchains/gcc-4.5.2-armv7l-maverick-cbuild93-ursa1-cortexa8r1/bin/gcc -O2 align.c ; ./a.out (nothing) michaelh@ursa2:~/linaro/bugs$ /tools/toolchains/gcc-4.6.0-armv7l-maverick-cbuild93-ursa1-cortexa8r1/bin/gcc -O2 align.c ; ./a.out (nothing) michaelh@ursa2:~/linaro/bugs$ ~/linaro/toolchains/gcc-4.7~svn174044-armv7l-maverick-cbuild120-ursa4-cortexa9r1/bin/gcc -O2 align.c ; ./a.out (nothing) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
Is this still an issue with 4.6? Need to understand implications of this for the release please. ** Changed in: gcc-4.5 (Ubuntu Oneiric) Assignee: (unassigned) => Linaro Tool Chain Working Group (linaro-toolchain-wg) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
Hi Ken. I'm not surprised by the results above. At all optimisation levels, GCC knows the alignment of a variable and therefore knows the value of the lower bits. At -O0 'foo' works as this information isn't propagated to the next line. 'thumb' fails as the value and alignment are available right there in the expression. -O2 is as expected. 'foo' is different as the value propagates to the fp & 0x1L expression. Note that the work-around of pushing the value through the getfp() function works correctly. GCC is still wrong though... -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
As shown above this bug makes it a bit difficult to obtain the thumb marker. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
I see a very similar issue even with -O0 when using GCC 4.5.2-8ubuntu1
on my ARM board.
Here is a simple test:
$ cat test.c && gcc -O0 -Wall -Winline test.c -o test.bin && echo "O0:" &&
./test.bin && gcc -O2 -Wall -Winline test.c -o test.bin && echo "O2:" &&
./test.bin
#include
static long __attribute__ ((noinline))
getfp (void *p)
{
return (long) p;
}
static void __attribute__ ((noinline))
myfunc(long fp, long foo, long bar, long code, long thumb, long thumb2)
{
printf ("\tfp: 0x%lx\n", fp);
printf ("\tfoo:0x%lx\n", foo);
printf ("\tbar:0x%lx\n", bar);
printf ("\tcode: 0x%lx\n", code);
printf ("\tthumb: 0x%lx\n", thumb);
printf ("\tthumb2: 0x%lx\n", thumb2);
}
int main()
{
long fp = (long) myfunc;
long foo = fp & 0x1L;
long bar = getfp (myfunc);
long code = (long) myfunc & ~0x1L;
long thumb = (long) myfunc & 0x1L;
long thumb2 = getfp (myfunc) & 0x1L;
myfunc(fp, foo, bar, code, thumb, thumb2);
return 0;
}
O0:
fp: 0x83b1
foo:0x1
bar:0x83b1
code: 0x83b0
thumb: 0x0
thumb2: 0x1
O2:
fp: 0x83a1
foo:0x0
bar:0x83a1
code: 0x83a0
thumb: 0x0
thumb2: 0x1
The interesting thing is the " (long) myfunc & 0x1L".
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[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
Changing bug to Won't Fix for Natty and retargetting to Oneiric.If this can not be worked around, please update status back to confirmed, and will work with teams to see what options are possible. ** Also affects: gcc-4.5 (Ubuntu Oneiric) Importance: Undecided Status: New ** Changed in: gcc-4.5 (Ubuntu Oneiric) Status: New => Triaged ** Changed in: gcc-4.5 (Ubuntu Oneiric) Importance: Undecided => High ** Changed in: gcc-4.5 (Ubuntu Natty) Status: Triaged => Won't Fix -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
** Changed in: gcc-4.5 (Ubuntu Natty) Assignee: (unassigned) => Linaro Tool Chain Working Group (linaro-toolchain-wg) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
I'm fairly sure this exists in FSF 4.5 but will confirm. FSF bugs are are lower priority to us and we're a bit swamped at the moment so I'm afraid this may not be fixed soon. A work around would be to break GCC's knowledge of the alignment of the variable. Passing it through another function would do it, but there's probably a better way too. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
@Steve: if you want GDB to give the true function address use '*main' - 'main' will give the first address after the prologue (at least when setting breakpoints, it does). @Michael: I think casting pointers from one pointer type to another (type punning) is deeply dodgy due to strict-aliasing rules, but I don't think converting them to integers is a problem (provided they are the same width). The bug here appears to be that GCC assumes that function pointer are always aligned, but fails to realise that thumb function pointers are always aligned+1, so to speak. I don't think it will be too hard to fix it. (Of course, fixing GCC so it's consistent probably won't help mono - that'll still need a fix. In my experience, this concept of off-by-one pointers breaks many, many things in 'interesting' ways.) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
Confirmed in Linaro GCC 4.5-2011.02-0. I assume that GCC is looking at
the type, checking the expected alignment, and then inferring what the
value of the LSB should be. This code:
extern int foo;
void main()
{
void *p = &foo;
if ((int)p & 1) printf ("HIT!\n");
}
gets optimised away into a bx lr as an int should be word aligned, so
the lower two bits should be zero. This code:
extern char foo;
void main()
{
void *p = &foo;
if ((int)p & 1) printf ("HIT!\n");
}
doesn't get optimised away as foo could be at an odd address.
I can't remember if casting a function pointer to an int is undefined
behaviour. I think it is, so this code is invalid. However it is very
useful so I think we should support it.
** Changed in: gcc-linaro
Status: Confirmed => Triaged
** Changed in: gcc-linaro
Importance: Undecided => Medium
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Title:
[armel] gcc computes wrong address for main() at build time
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[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
@paul: the address will be changing due to the code before it changing at different optimisation levels. The important thing is that in ARM mode the LSB is clear, while in Thumb mode the LSB is set in all situations. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
@steve: GDB has set the breakpoint at the first interesting instruction after the prologue, which is fine. GCC seems to be correct - if you want to jump to main, you want to jump to address 0x8390 in Thumb mode (i.e. LSB set). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
Not sure if this is relevant, but I seem to be seeing something slightly different. I also added a printf to see what it thinks the value of p is, and tested this with gcc-4.3, 4.4, 4.5: gcc version 4.3.5 (Ubuntu 4.3.5-3ubuntu1) without -O2: p=0x83e0 with -O2: p=0x83e0 gcc version 4.4.5 (Ubuntu/Linaro 4.4.5-11ubuntu1) without -O2: HIT! p=0x83c1 with -O2: HIT! p=0x83c5 gcc version 4.5.2 (Ubuntu/Linaro 4.5.2-3ubuntu1) without -O2: HIT! p=0x83c1 with -O2: p=0x8399 gcc-4.3 was the only consistent one, but it did not have -mthumb enabled by default. with gcc-4.3 -mthumb, I get the same thing with or without using -O2: HIT! p=0x83e1 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] gcc computes wrong address for main() at build time
This is reproducible with gcc-4.5 4.5.1-8ubuntu2, the version being used at natty open. So it seems to be a longstanding bug. Not reproducible when building with -O1 or -O2 because gcc optimizes the code out completely (getting the right answer for the address of main in this case... or at least the right parity). Not reproducible when building with -marm. ** Summary changed: - [armel] Confirmed toolchain regression when using & in an if statement on a function + [armel] gcc computes wrong address for main() at build time ** Also affects: gcc-linaro Importance: Undecided Status: New ** Changed in: gcc-4.5 (Ubuntu Natty) Status: Confirmed => Triaged ** Changed in: gcc-linaro Status: New => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] Confirmed toolchain regression when using & in an if statement on a function
So the issue isn't that & is working incorrectly, the issue is that the address of main according to gcc is given as 0x8391 and this seems to not be what we want. (gdb has a different idea of main's address, for instance - 0x8396.) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] gcc computes wrong address for main() at build time -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] Confirmed toolchain regression when using & in an if statement on a function
Here's what gdb shows:
Breakpoint 1, main () at testcase.c:4
4 void *p = main;
(gdb) disas
Dump of assembler code for function main:
0x8390 <+0>: push{r7, lr}
0x8392 <+2>: sub sp, #8
0x8394 <+4>: add r7, sp, #0
=> 0x8396 <+6>: movwr3, #33681 ; 0x8391
0x839a <+10>:movtr3, #0
0x839e <+14>:str r3, [r7, #4]
0x83a0 <+16>:ldr r3, [r7, #4]
0x83a2 <+18>:and.w r3, r3, #1
0x83a6 <+22>:uxtbr3, r3
0x83a8 <+24>:cmp r3, #0
0x83aa <+26>:beq.n 0x83b8
0x83ac <+28>:movwr0, #33808 ; 0x8410
0x83b0 <+32>:movtr0, #0
0x83b4 <+36>:blx 0x8304
0x83b8 <+40>:add.w r7, r7, #8
0x83bc <+44>:mov sp, r7
0x83be <+46>:pop {r7, pc}
End of assembler dump.
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[armel] Confirmed toolchain regression when using & in an if statement
on a function
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[Bug 721531] Re: [armel] Confirmed toolchain regression when using & in an if statement
Disregard it affecting on x86, false-positive as it also still occurs with -O0 on that platform. ** Tags added: armel ** Changed in: gcc-4.5 (Ubuntu) Status: New => Confirmed ** Changed in: gcc-4.5 (Ubuntu) Importance: Undecided => High ** Also affects: gcc-4.5 (Ubuntu Natty) Importance: High Status: Confirmed ** Summary changed: - [armel] Confirmed toolchain regression when using & in an if statement + [armel] Confirmed toolchain regression when using & in an if statement on a function -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] Confirmed toolchain regression when using & in an if statement on a function -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] Re: [armel] Confirmed toolchain regression when using & in an if statement
Amendment: Also occurs on amd64 mcasadevall@daybreak:/tmp$ uname -a Linux daybreak 2.6.38-2-generic #29-Ubuntu SMP Fri Feb 4 13:03:04 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux mcasadevall@daybreak:/tmp$ gcc -O2 test.c test.c: In function ‘main’: test.c:3:13: warning: cast from pointer to integer of different size test.c:3:25: warning: incompatible implicit declaration of built-in function ‘printf’ -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/721531 Title: [armel] Confirmed toolchain regression when using & in an if statement -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 721531] [NEW] [armel] Confirmed toolchain regression when using & in an if statement
Public bug reported:
Binary package hint: gcc-4.5
During the debugging of mono, we found a confirmed tool chain regression
and isolated it down to a testcase:
Test code:
void main() {
void *p = main;
if ((int)p & 1) printf ("HIT!\n");
}
Output:
mcasadevall@risingsun:~/tmp$ gcc -g test.c
test.c: In function 'main':
test.c:3:18: warning: incompatible implicit declaration of built-in function
'printf'
mcasadevall@risingsun:~/tmp$ ./a.out
HIT!
mcasadevall@risingsun:~/tmp$ gcc -g -O2 test.c
test.c: In function 'main':
test.c:3:18: warning: incompatible implicit declaration of built-in function
'printf'
mcasadevall@risingsun:~/tmp$ ./a.out
mcasadevall@risingsun:~/tmp$
Doesn't occur with gcc-4.4.
Additional comments from #monodev:
16:26:58 < vargaz> NCommander: it seems to think function addresses on arm
have their lowest bit set to 0, which is not true for
thumb.
** Affects: gcc-4.5 (Ubuntu)
Importance: Undecided
Status: New
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[armel] Confirmed toolchain regression when using & in an if statement
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