[Bug tree-optimization/92879] [10 Regression] incorrect warning of __builtin_memset offset is out of the bounds on zero-size allocation and initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #6 from Jakub Jelinek --- The placement new is inlined at this point, the operator new that remains is replaceable and because a is a global variable, its address needs to be considered escaped. While access to not yet fully constructed var from another TU might be problematic, in what the restrict pass we actually don't know (unless we look at abstract origin and prove there is no post-ctor code in between) it is a ctor which would have such restrictions.
[Bug tree-optimization/92879] [10 Regression] incorrect warning of __builtin_memset offset is out of the bounds on zero-size allocation and initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879 Jeffrey A. Law changed: What|Removed |Added Priority|P3 |P2 CC||law at redhat dot com
[Bug tree-optimization/92879] [10 Regression] incorrect warning of __builtin_memset offset is out of the bounds on zero-size allocation and initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879 Richard Biener changed: What|Removed |Added Keywords||missed-optimization CC||rguenth at gcc dot gnu.org --- Comment #5 from Richard Biener --- There's eventually the possibility to adjust call_may_clobber_ref_p_1 to handle calls that are DECL_IS_REPLACEABLE_OPERATOR_NEW_P specially. Not sure why that is "replaceable" but you mention new is not replaceable... Ah, there's also DECL_IS_OPERATOR_NEW_P (but docs say it's to be used for alias analysis on the resulting ptr).
[Bug tree-optimization/92879] [10 Regression] incorrect warning of __builtin_memset offset is out of the bounds on zero-size allocation and initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879 --- Comment #4 from Martin Sebor --- After some more thought I think I need to correct myself: I suppose even in a ctor the this pointer might need to be treated as having escaped and be accessible to a replacement operator new, but placement new is not replaceable so it can't access such an escaped pointer.
[Bug tree-optimization/92879] [10 Regression] incorrect warning of __builtin_memset offset is out of the bounds on zero-size allocation and initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879
Martin Sebor changed:
What|Removed |Added
Keywords||alias
Blocks||56456
--- Comment #3 from Martin Sebor ---
The warning sees the IL below so it's doing the right thing. GCC doesn't
"know" that operator new doesn't clobber this->m so it doesn't eliminate the
for loop. Rewriting the loop like so avoids the warning and results in optimal
code equivalent to that emitted by Clang:
for(int j=0;j [local count: 1073741824]:
MEM[(struct &)&a] ={v} {CLOBBER};
a.m = 0;
_5 = operator new [] (0);
a.p = _5;
_2 = a.m; <<< unnecessary: _2 must be 0
if (_2 <= 0)
goto ; [11.00%]
else
goto ; [89.00%]
[local count: 955630224]:
_20 = (unsigned int) _2;
_12 = _20 + 4294967295;
_6 = (sizetype) _12;
_21 = (sizetype) _2;
_7 = _21 * 4;
__builtin_memset (_5, 0, _7);
[local count: 1073741833]:
return;
}
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56456
[Bug 56456] [meta-bug] bogus/missing -Warray-bounds
[Bug tree-optimization/92879] [10 Regression] incorrect warning of __builtin_memset offset is out of the bounds on zero-size allocation and initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92879 Martin Liška changed: What|Removed |Added Status|UNCONFIRMED |NEW Last reconfirmed||2019-12-10 CC||marxin at gcc dot gnu.org, ||msebor at gcc dot gnu.org Known to work||9.2.0 Target Milestone|--- |10.0 Summary|incorrect warning of|[10 Regression] incorrect |__builtin_memset offset is |warning of __builtin_memset |out of the bounds on|offset is out of the bounds |zero-size allocation and|on zero-size allocation and |initialization |initialization Ever confirmed|0 |1 Known to fail||10.0 --- Comment #2 from Martin Liška --- Confirmed, started with r278983.
