[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597 --- Comment #7 from Jan Hubicka --- So I guess it is asan being confused by our optimization. We intentionaly duplicate the symbol in order to reduce cost of dynamic linking in situations where we know it does not change semantics, but asan looks for such duplicates and consider them ODR violations. I guess we want to disable the optimization with -fsanitize-address. I will try to cook up a patch.
[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597 Martin Liška changed: What|Removed |Added Assignee|marxin at gcc dot gnu.org |unassigned at gcc dot gnu.org Status|ASSIGNED|NEW --- Comment #6 from Martin Liška --- > So this is kind of feature. How the ODR violations are detected? > I wonder if keeping weak flag disturbs something. ASAN emits so-called ODR indicators for all global symbols that survive the following check: asan_needs_odr_indicator_p (tree decl) in asan.cc:3216 And that's we see 2 of them: marxin@marxinbox:~/Programming/testcases/PR107597> nm libTest1.so | grep odr 40c0 B __odr_asan._ZN12NonTemplated1xE marxin@marxinbox:~/Programming/testcases/PR107597> nm libTest2.so | grep odr 40c0 B __odr_asan._ZN12NonTemplated1xE which eventually ends up with the run-time error.
[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597 --- Comment #5 from Martin Liška --- > > So this is kind of feature. How the ODR violations are detected? ASAN emits > I wonder if keeping weak flag disturbs something.
[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597 Martin Liška changed: What|Removed |Added Assignee|unassigned at gcc dot gnu.org |marxin at gcc dot gnu.org CC||marxin at gcc dot gnu.org Status|NEW |ASSIGNED --- Comment #4 from Martin Liška --- I'll take a look at why it's not caught by ASAN.
[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597
--- Comment #3 from Christoph Steefel ---
Address sanitizer is the one that flags it.
This is the code I used to reproduce the failure.
test.h:
class NonTemplated {
static inline int x;
public:
void doFoo() {
x++;
}
};
int foo();
int bar();
test1.cpp:
#include "test.h"
int foo() {
NonTemplated n;
n.doFoo();
return 1;
}
test2.cpp:
#include "test.h"
int bar() {
NonTemplated n;
n.doFoo();
return 1;
}
main.cpp:
#include "test.h"
int main(){
foo();
bar();
return 0;
}
> g++ -shared -o libTest1.so -flto -fsemantic-interposition -fPIC test1.cpp
> -fsanitize=address
> g++ -shared -o libTest2.so -flto -fsemantic-interposition -fPIC test2.cpp
> -fsanitize=address
> g++ -shared -o libMain.so -flto -fsemantic-interposition -fPIC main.cpp
> -fsanitize=address
> g++ libMain.so libTest1.so libTest2.so -fsanitize=address
> LD_LIBRARY_PATH=. ./a.out
=
==9794==ERROR: AddressSanitizer: odr-violation (0x7f6340a3d0e0):
[1] size=4 'x' test.h:2:22
[2] size=4 'x' test.h:2:22
... (backtrace elided)
My general understanding is that address sanitizer doesn't instrument weak or
unique symbols, but will clearly instrument the non-weak symbol here.
[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597 --- Comment #2 from Jan Hubicka --- Hi, What happens is that we read the symbol as: Visibility: externally_visible semantic_interposition prevailing_def_ironly_exp public weak comdat comdat_group:_ZN12NonTemplated1xE one_only While in visibility pass we promote it to: Visibility: externally_visible semantic_interposition prevailing_def_ironly_exp public comdat So we disolve comdat group and turn off weak. This leads to better code generation and we know it does not affect dynamic linking since in shared library all symbols are interposable. So this is kind of feature. How the ODR violations are detected? I wonder if keeping weak flag disturbs something.
[Bug c++/107597] LTO causes static inline variables to get a non-uniqued global symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107597 Richard Biener changed: What|Removed |Added CC||amodra at gcc dot gnu.org, ||hubicka at gcc dot gnu.org, ||jason at gcc dot gnu.org, ||rguenth at gcc dot gnu.org Ever confirmed|0 |1 Last reconfirmed||2022-11-10 Keywords||lto, wrong-code Status|UNCONFIRMED |NEW --- Comment #1 from Richard Biener --- 1 libFoo.so-t.o 2 192 c3d22ca2af7ab12c PREVAILING_DEF_IRONLY_EXP main 197 c3d22ca2af7ab12c PREVAILING_DEF_IRONLY_EXP _ZN12NonTemplated1xE confirmed (binutils 2.37). I think the above shows the linker doesn't properly communicate the uniqueness but we might be able to recover from the bits we have in the streamed IL?
