[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] 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] 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/4.5 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
** 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
** 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
** 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
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 Klose d...@ubuntu.com Thu, 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
** 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 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] 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
** 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] 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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[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
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
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
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
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:
snip
$ 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 stdio.h
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
/snip
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
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
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
** 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
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
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
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] 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
@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
@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
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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