Hi list,
I hit another weird problem after use gcc 5.3 (If I use gcc 4.9, there is no any
issue) with android.
With arm gcc 5.3, the C++ apps crash in one class constructor call. And gdb
shows some vtbl items of the class are not relocated.
With arm gcc 4.9, if set breakpoint in that constructor, we could see the vtbl
items of the class are relocated.
And Yes. I know the android bionic loader take response to do relocation. But if
it works with gcc 4.9, I suppose bionic loader work well (unless gcc 5.3 create
some new situation not handled by it).
I attached the vtbl dump in gdb for gcc 5.3 and 4.9 both. We could see all valid
entries in vtbl are relocated in 4.9 dump. But not all entries in vtbl are
relocated in 5.3 dump (the address is not started with 0xf).
Suggestions/hints are welcome. Thanks a lot.
Regards
Yin, Fengwei
On Thu, Mar 31, 2016 at 5:12 AM, fengwei.yin <fengwei.yin(a)linaro.org> wrote:
> Because gcc 4.9 could build this file without any issue, I apply
> --save-temps
> with gcc 4.9. The ii file is attached. Can't see significant differences.
There is a patch in gcc-5 to make unified assembler syntax the
default. Unfortunately, it changes how extended asms work, which is
perhaps a bug. The message claims it doesn't affect extended asms,
but it does.
https://gcc.gnu.org/ml/gcc-patches/2015-11/msg01196.html
The interesting bit is the change to ASM_APP_OFF.
gcc-4.9 emits a .thumb after the extended asm to switch back into
thumb mode just in case. gcc-5.3 instead emits .syntax unified, which
doesn't change the arm/thumb mode, just the syntax supported. This is
arguably a bug, but this doesn't immediately help you. It could take
a little time to get gcc-5.x source fixed, and then the compiler
binary releases. Or alternatively we could fix the asm to work with
gcc 5.
Jim
== Progress ==
o Extended validation (7/10)
* Fixed and improved extended native validation
* Discussed proposed patch in dejagnu on process killing mechanism
* Testing a fix/workaround in GCC guality tests
* Re-implemented and tested fix for dejagnu remote layout
o Misc (3/10)
* Various meetings
== Plan ==
o Continue on extended validation
o Finalize DejaGNU patches, GCC ARMv8.1 builtins fix.
== This week ==
* Bugzilla 69008 - gcc emits unneeded memory access when passing trivial
structs by value (ARM) (3/10)
- Additional investigation and preliminary implementation
* Bugzilla 70089 - ARM/THUMB unnecessarily typecasts some rvalues on
memory store (1/10)
- Investigation
* TCWG-247 - Create Validation Job to run on GCC Trunk Committ (5/10)
- Began writing shell script.
* Misc meeting (1/10)
== Next week ==
* TCWG-247
- Make additional prgoress on prototype
* Bugzilla 69008 - gcc emits unneeded memory access when passing trivial
structs by value (ARM)
- Additional investigation and preliminary implementation
* Bugzilla 70089 - ARM/THUMB unnecessarily typecasts some rvalues on
memory store
- Investigation
* Vacation
- April 8 - April 12
== Progress ==
* Holiday (2/10)
* Support (1/10)
- Reapplying fix for PR16275 (D18701)
- Conclusion is that original approach will be the same as GCC
- Additional flags will have to be agreed upon across compilers
* Buildbot (2/10)
- Setting up LLDB buildbot with Omair
- Precarious infrastructure is unstable, hope it holds on until the
new rack is complete
* Background (5/10)
- Code review, meetings, discussions, general support, etc.
- More team management stuff (access/procedure/meeting with newcomers)
- Planning the lab move, resources, costs, schedule
* Monday off [2/10]
# Progress #
* TCWG-167, ARM reverse debugging bug fixes. [4/10]
Two patches are posted. Two patches are being tested. They fix
207 FAILs (242 -> 35) in gdb.reverse.
* TCWG-545, no progress, patches are pending for review.
* TCWG-547, [2/10]. Write a patch as Pedro suggested, so we have
sense which patch is better. No response.
* Misc, [2/10]
** Upstream discussions on get syscall number on execve exit. Can't
get such thing from kernel side, need to figure out how to do it
in GDB side.
** Investigate a little bit on 32-bit DWARF on AArch64.
# Plan #
* TCWG-167, TCWG-545, TCWG-547
--
Yao
== This Week ==
* LTO (7/10)
a) TCWG-534 (ipa-comdats):
- Patch posted upstream: https://gcc.gnu.org/ml/gcc/2016-03/msg00254.html
- Investigating ICE with patch for comdat-2.C
b) TCWG-128 (branch out of range error):
- Posted patch upstream:
https://gcc.gnu.org/ml/gcc-patches/2016-04/msg00032.html
c) intra-procedural vrp:
- Looking to implement replacement_order algorithm for early vrp from the paper:
https://engineering.purdue.edu/paramnt/publications/1381.pdf
* Validation (2/10)
- Reviews on tcwg-buildapp from Christophe and Maxim
- prototype job ran successfully.
* Misc (1/10)
- Meetings
== Next Week ==
* LTO:
- Try to implement replacement order algorithm for vrp
- Continue investigating ipa-comdats ICE and address upstream comments.
- Gather stats for chromium LTO build
* Validation:
- write script to build chromium
