Hi!
As mentioned in the PR, _gfortran_{,m,s}findloc2_s{1,4} iterate too many
times in the back case if nothing is found.
For !back, the loops are for (i = 1; i <= extent; i++) so i is in the
body [1, extent] if nothing is found, but for back it is
for (i = extent; i >= 0; i--) so i is in the body [0, extent] and compares
one element before the start of the array.
Note, findloc1_s{1,4} uses
for (n = len; n > 0; n--, src -= delta * len_array)
for the back loop and
for (n = 1; n <= len; n++, src += delta * len_array)
for !back. This patch fixes that.
The testcase fails under valgrind without the libgfortran changes and
succeeds with those.
Tested on x86_64-linux and i686-linux, ok for trunk?
2025-05-13 Jakub Jelinek <ja...@redhat.com>
PR libfortran/120196
* m4/ifindloc2.m4 (header1, header2): For back use i > 0 rather than
i >= 0 as for condition.
* generated/findloc2_s1.c: Regenerate.
* generated/findloc2_s4.c: Regenerate.
* gfortran.dg/pr120196.f90: New test.
--- libgfortran/m4/ifindloc2.m4.jj 2025-01-02 20:54:32.795120703 +0100
+++ libgfortran/m4/ifindloc2.m4 2025-05-13 09:49:03.169899035 +0200
@@ -41,7 +41,7 @@ see the files COPYING3 and COPYING.RUNTI
if (back)
{
src = array->base_addr + (extent - 1) * sstride;
- for (i = extent; i >= 0; i--)
+ for (i = extent; i > 0; i--)
{
if ('comparison`'`)
return i;
@@ -94,7 +94,7 @@ see the files COPYING3 and COPYING.RUNTI
{
src = array->base_addr + (extent - 1) * sstride;
mbase += (extent - 1) * mstride;
- for (i = extent; i >= 0; i--)
+ for (i = extent; i > 0; i--)
{
if (*mbase && ('comparison`'`))
return i;
--- libgfortran/generated/findloc2_s1.c.jj 2025-01-02 20:54:32.759121201
+0100
+++ libgfortran/generated/findloc2_s1.c 2025-05-13 09:49:40.040393417 +0200
@@ -49,7 +49,7 @@ findloc2_s1 (gfc_array_s1 * const restri
if (back)
{
src = array->base_addr + (extent - 1) * sstride;
- for (i = extent; i >= 0; i--)
+ for (i = extent; i > 0; i--)
{
if (compare_string (len_array, (char *) src, len_value, (char *)
value) == 0)
return i;
@@ -112,7 +112,7 @@ mfindloc2_s1 (gfc_array_s1 * const restr
{
src = array->base_addr + (extent - 1) * sstride;
mbase += (extent - 1) * mstride;
- for (i = extent; i >= 0; i--)
+ for (i = extent; i > 0; i--)
{
if (*mbase && (compare_string (len_array, (char *) src, len_value,
(char *) value) == 0))
return i;
--- libgfortran/generated/findloc2_s4.c.jj 2025-01-02 20:54:32.759121201
+0100
+++ libgfortran/generated/findloc2_s4.c 2025-05-13 09:49:49.280266714 +0200
@@ -49,7 +49,7 @@ findloc2_s4 (gfc_array_s4 * const restri
if (back)
{
src = array->base_addr + (extent - 1) * sstride;
- for (i = extent; i >= 0; i--)
+ for (i = extent; i > 0; i--)
{
if (compare_string_char4 (len_array, src, len_value, value) == 0)
return i;
@@ -112,7 +112,7 @@ mfindloc2_s4 (gfc_array_s4 * const restr
{
src = array->base_addr + (extent - 1) * sstride;
mbase += (extent - 1) * mstride;
- for (i = extent; i >= 0; i--)
+ for (i = extent; i > 0; i--)
{
if (*mbase && (compare_string_char4 (len_array, src, len_value,
value) == 0))
return i;
--- gcc/testsuite/gfortran.dg/pr120196.f90.jj 2025-05-13 09:48:32.331321930
+0200
+++ gcc/testsuite/gfortran.dg/pr120196.f90 2025-05-13 09:54:12.639655187
+0200
@@ -0,0 +1,26 @@
+! PR libfortran/120196
+! { dg-do run }
+
+program pr120196
+ character(len=:, kind=1), allocatable :: a(:), s
+ character(len=:, kind=4), allocatable :: b(:), t
+ logical, allocatable :: l(:)
+ logical :: m
+ allocate (character(len=16, kind=1) :: a(10), s)
+ allocate (l(10))
+ a(:) = ""
+ s = "*"
+ l = .true.
+ m = .true.
+ if (findloc (a, s, dim=1, back=.true.) .ne. 0) stop 1
+ if (findloc (a, s, mask=l, dim=1, back=.true.) .ne. 0) stop 2
+ if (findloc (a, s, mask=m, dim=1, back=.true.) .ne. 0) stop 3
+ deallocate (a, s)
+ allocate (character(len=16, kind=4) :: b(10), t)
+ b(:) = ""
+ t = "*"
+ if (findloc (b, t, dim=1, back=.true.) .ne. 0) stop 4
+ if (findloc (b, t, mask=l, dim=1, back=.true.) .ne. 0) stop 5
+ if (findloc (b, t, mask=m, dim=1, back=.true.) .ne. 0) stop 6
+ deallocate (b, t, l)
+end program pr120196
Jakub
