[Bug ipa/105438] [11/12/13/14 Regression] Incorrect array-bounds warning with array size carried over from a previous template instantiation since r11-4987-g602c6cfc79ce4ae6
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 Bernie Innocenti changed: What|Removed |Added Version|11.3.0 |13.1.1 Target Milestone|11.5|13.2 --- Comment #13 from Bernie Innocenti --- Still present on g++ 13.1.1 I discovered that -O2 is required to trigger this bug. These compile without warnings: g++ -O1 -Warray-bounds repro.cc g++ -O3 -Warray-bounds repro.cc g++ -Ofast -Warray-bounds repro.cc
[Bug ipa/105438] [11/12/13 Regression] Incorrect array-bounds warning with array size carried over from a previous template instantiation since r11-4987-g602c6cfc79ce4ae6
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 --- Comment #10 from Bernie Innocenti --- Still present on GCC 12.2. Could someone look into it please, or point me at the point in ipa-icf.cc where the array-bounds analysis information should have been updated after merging the template instantiations?
[Bug c++/105438] Incorrect array-bounds warning with array size carried over from a previous template instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 --- Comment #4 from Bernie Innocenti --- Furthermore, after the inline pass main() has a reference to the shorter array with an annotation of int[7], which is clearly wrong: [local count: 939524097]: _5 = MEM[(const int[7] &)][i_4]; out[i_4] = _5; i_6 = i_4 + 1;
[Bug c++/105438] Incorrect array-bounds warning with array size carried over from a previous template instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 --- Comment #3 from Bernie Innocenti --- Not sure if this is helpful, but the IPA dump also shows two calls to configure() with N=7 and none with N=2: IPA function summary for int main()/3 inlinable global time: 26.00 self size: 9 global size: 9 min size: 6 self stack: 0 global stack:0 size:0.00, time:0.00 size:3.00, time:2.00, executed if:(not inlined) calls: void configure(const int (&)[N], int) [with int N = 7]/6 function not considered for inlining freq:1.00 loop depth: 0 size: 3 time: 12 callee size: 5 stack: 0 op0 is compile time invariant op1 is compile time invariant void configure(const int (&)[N], int) [with int N = 7]/6 function not considered for inlining freq:1.00 loop depth: 0 size: 3 time: 12 callee size: 5 stack: 0 op0 is compile time invariant op1 is compile time invariant
[Bug c++/105438] Incorrect array-bounds warning with array size carried over from a previous template instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 --- Comment #2 from Bernie Innocenti --- GCC 12.0.1 20220413 (Red Hat 12.0.1-0) gives a more helpful diagnostic with inlining backtrace: In function ‘void configure(const int (&)[N], int) [with int N = 7]’, inlined from ‘void configure(const int (&)[N], int) [with int N = 2]’ at testcase.cc:8:6, inlined from ‘int main()’ at gcc-array-bounds-bug-testcase.cc:22:12: testcase.cc:14:24: warning: array subscript ‘const int [7][0]’ is partly outside array bounds of ‘int [2]’ [-Warray-bounds] 14 | out[i] = in[i]; | ~~^ Note how configure() was inlined into configure().
[Bug c++/105438] Incorrect array-bounds warning with array size carried over from a previous template instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438 --- Comment #1 from Bernie Innocenti --- Reproducible in Godbolt with any 11.x release as well as trunk: https://godbolt.org/z/zWb55P8G7
[Bug c++/105438] New: Incorrect array-bounds warning with array size carried over from a previous template instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105438
Bug ID: 105438
Summary: Incorrect array-bounds warning with array size carried
over from a previous template instantiation
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: bernie at codewiz dot org
Target Milestone: ---
Minified testcase (almost every line is necessary to reproduce):
```
/* g++ -Warray-bounds -O2 repro.cc */
int longer[7] = {};
int shorter[2] = {};
int out[10] = {};
template
void configure(const int()[N], const int nrows = N)
{
if (nrows <= 10)
{
for (int i = 0; i < nrows; i++)
{
out[i] = in[i];
}
}
}
int main()
{
configure(longer);
configure(shorter);
}
```
Output:
```
$ g++ -Warray-bounds -O2 repro.cc
repro.cc: In function 'int main()':
repro.cc:13:24: warning: array subscript 'const int [7][0]' is partly outside
array bounds of 'int [2]' [-Warray-bounds]
13 | out[i] = in[i];
| ~~^
repro.cc:3:5: note: while referencing 'shorter'
3 | int shorter[2] = {};
| ^~~
repro.cc:13:24: warning: array subscript 'const int [7][0]' is partly outside
array bounds of 'int [2]' [-Warray-bounds]
13 | out[i] = in[i];
| ~~^
repro.cc:3:5: note: while referencing 'shorter'
3 | int shorter[2] = {};
| ^~~
```
Static analysis appears to be using the length of the longer array for the call
using the shorter array.
The warning disappears by:
* commenting out the first call to configure() suppresses the warning
* swapping the two calls to configure()
* commenting out if statement also eliminates the warning
* making longer and shorter the same size
* using N as loop counter instead of nrows
[Bug c++/98824] [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824 --- Comment #4 from Bernie Innocenti --- Are there any known workarounds?
[Bug c++/98824] [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824 Bernie Innocenti changed: What|Removed |Added CC||bernie at codewiz dot org --- Comment #3 from Bernie Innocenti --- Assuming this is the same bug, it's still present in g++ 12 as well as trunk: https://godbolt.org/z/6r3bc3j15
[Bug c++/79001] spurious "defined but not used" warning with explicit instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79001 --- Comment #5 from Bernie Innocenti --- clang with -Wunused-function also does not issue a warning for this testcase.
[Bug c++/79001] spurious "defined but not used" warning with explicit instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79001 --- Comment #4 from Bernie Innocenti --- GCC 5.1 does not issue a warning.
[Bug c++/79001] spurious "defined but not used" warning with explicit instantiation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79001 Bernie Innocenti changed: What|Removed |Added CC||bernie at codewiz dot org --- Comment #3 from Bernie Innocenti --- Same behavior on GCC 11.2
