On 9/30/21 9:14 PM, Mathieu Desnoyers wrote:
**[Please note: This e-mail is from an EXTERNAL e-mail address]
----- On Sep 29, 2021, at 11:47 PM, lttng-dev
<lttng-dev@lists.lttng.org> wrote:
Hi,
The problem happened after upgrade to lttng-ust 2.13.0. 2.12.0
don't have this issue.
liburcu version: 0.13.0
gcc: 11.2.0
This is my reproduce steps, it is cross compile enviroment based
on yocto project.
1. git clone git://git.yoctoproject.org/poky
2. . oe-init-build-env
3. echo "MACHINE='qemuarm'" >> conf/local.conf
4. echo "DEBUG_BUILD='1'" >> conf/local.conf
5. bitbake lttng-ust
compile failed with error:
|
/work/cortexa15t2hf-neon-poky-linux-gnueabi/lttng-ust/2_2.13.0-r0/recipe-sysroot-native/usr/bin/arm-poky-linux-gnueabi/../../libexec/arm-poky-linux-gnueabi/gcc/arm-poky-linux-gnueabi/11.2.0/ld:
../../../src/lib/lttng-ust/.libs/liblttng-ust.so
<https://urldefense.com/v3/__http://liblttng-ust.so__;!!AjveYdw8EvQ!LLTouw-mBEBAY8hObF75ydNA3D3KMc0Hla12A4D4cQ-hm-F5lidnggb4zDVbAwolB77-gw$>:
undefined reference to `_uatomic_link_error'
| collect2: error: ld returned 1 exit status
| Makefile:399: recipe for target 'test_ust_error' failed
checked with "nm ../../../src/lib/lttng-ust/.libs/liblttng-ust.so
<https://urldefense.com/v3/__http://liblttng-ust.so__;!!AjveYdw8EvQ!LLTouw-mBEBAY8hObF75ydNA3D3KMc0Hla12A4D4cQ-hm-F5lidnggb4zDVbAwolB77-gw$>"
| grep atomic, we can see 'U _uatomic_link_error', but since -Og
is used, liburcu don't define this function.
[snip]
#if !defined __OPTIMIZE__ || defined UATOMIC_NO_LINK_ERROR
static inline __attribute__((always_inline, noreturn))
void _uatomic_link_error(void)
{
#ifdef ILLEGAL_INSTR
/*
* generate an illegal instruction. Cannot catch this with
* linker tricks when optimizations are disabled.
*/
__asm__ __volatile__(ILLEGAL_INSTR);
#else
__builtin_trap();
#endif
}
#else /* #if !defined __OPTIMIZE__ || defined
UATOMIC_NO_LINK_ERROR */
extern void _uatomic_link_error(void);
#endif /* #else #if !defined __OPTIMIZE__ || defined
UATOMIC_NO_LINK_ERROR */
[snip]
we cannot see 'U _uatomic_link_error' in following conditions, so
compile successed:
1. without -Og(using -O2), + 32bit arm
2. -Og + 64bit arm
3. -Og + x86/x86-64
Do you have any idea about how to fix this? I don't understand why
only "-Og + 32bit arm" will call function _uatomic_link_error.
I suspect it depends on which optimizations are being enabled at -Og
on each architecture.
The "_uatomic_link_error()" trick indeed depends on the compiler
optimizing away
unreachable calls.
If you really intend on using "-Og" on arm32, trying building with
"-DUATOMIC_NO_LINK_ERROR".
It should take care of making sure to generate an illegal instruction
rather than rely on the linker
error.
Thanks,
Mathieu
Thanks. I have tried with "-DUATOMIC_NO_LINK_ERROR". With this, it
can compile successfully.
Changqing
Thanks
//Changqing
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--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
<https://urldefense.com/v3/__http://www.efficios.com__;!!AjveYdw8EvQ!LLTouw-mBEBAY8hObF75ydNA3D3KMc0Hla12A4D4cQ-hm-F5lidnggb4zDVbAwo9O85jiQ$>
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