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When libgfortran is compiled, there are some -Woverflow warnings like
../../../libgfortran/generated/maxloc0_4_m1.c:99:14: warning: unsigned conversion from ‘int’ to ‘GFC_UINTEGER_1’ {aka ‘unsigned char’} changes value from ‘-255’ to ‘1’ [-Woverflow]
99 | maxval = -GFC_UINTEGER_1_HUGE;
| ^
and those actually point a bug in the maxloc*/maxval* implementation
for UNSIGNED.
The intent of
#if defined ('atype_inf`)
result = -atype_inf;
#else
result = atype_min;
#endif
(or similar for maxval) is to initialize the variable with
minimum value of the type, if the type has infinities, then
negative infinity, otherwise the minimum (normalized) value.
atype_min expands for signed integers to say (-GFC_INTEGER_4_HUGE-1)
or for floating point to say -GFC_REAL_8_HUGE.
For UNSIGNED it expands to e.g. -GFC_UINTEGER_4_HUGE, but that is
-0xffffffffU which is 1U, while the minimum value of the type is
0.
Haven't tried to construct testcases for that, but I believe e.g.
maskval could return incorrectly 1 on an array (or masked array)
full of 0s, or maxloc could identify incorrectly the maximum location.
The following patch makes sure atype_min expands to 0 for atype_name
GFC_UINTEGER*.
2025-05-07 Jakub Jelinek <jakub@redhat.com>
PR libfortran/120158
* m4/iparm.m4 (atype_min): For atype_name starting with
GFC_UINTEGER define to 0.
* generated/maxloc0_16_m1.c: Regenerate.
* generated/maxloc0_16_m2.c: Regenerate.
* generated/maxloc0_16_m4.c: Regenerate.
* generated/maxloc0_16_m8.c: Regenerate.
* generated/maxloc0_16_m16.c: Regenerate.
* generated/maxloc0_4_m1.c: Regenerate.
* generated/maxloc0_4_m2.c: Regenerate.
* generated/maxloc0_4_m4.c: Regenerate.
* generated/maxloc0_4_m8.c: Regenerate.
* generated/maxloc0_4_m16.c: Regenerate.
* generated/maxloc0_8_m1.c: Regenerate.
* generated/maxloc0_8_m2.c: Regenerate.
* generated/maxloc0_8_m4.c: Regenerate.
* generated/maxloc0_8_m8.c: Regenerate.
* generated/maxloc0_8_m16.c: Regenerate.
* generated/maxloc1_16_m1.c: Regenerate.
* generated/maxloc1_16_m2.c: Regenerate.
* generated/maxloc1_16_m4.c: Regenerate.
* generated/maxloc1_16_m8.c: Regenerate.
* generated/maxloc1_16_m16.c: Regenerate.
* generated/maxloc1_4_m1.c: Regenerate.
* generated/maxloc1_4_m2.c: Regenerate.
* generated/maxloc1_4_m4.c: Regenerate.
* generated/maxloc1_4_m8.c: Regenerate.
* generated/maxloc1_4_m16.c: Regenerate.
* generated/maxloc1_8_m1.c: Regenerate.
* generated/maxloc1_8_m2.c: Regenerate.
* generated/maxloc1_8_m4.c: Regenerate.
* generated/maxloc1_8_m8.c: Regenerate.
* generated/maxloc1_8_m16.c: Regenerate.
* generated/maxval_m1.c: Regenerate.
* generated/maxval_m2.c: Regenerate.
* generated/maxval_m4.c: Regenerate.
* generated/maxval_m8.c: Regenerate.
* generated/maxval_m16.c: Regenerate.
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