From 9e80cfa14ed0bdec20361ae78e74ccb937de3428 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Sat, 18 Jan 2020 22:38:29 +0000 Subject: gdb/fortran: Support negative array stride in one limited case This commit adds support for negative Fortran array strides in one limited case, that is the case of a single element array with a negative array stride. The changes in this commit will be required in order for more general negative array stride support to work correctly, however, right now other problems in GDB prevent negative array strides from working in the general case. The reason negative array strides don't currently work in the general case is that when dealing with such arrays, the base address for the objects data is actually the highest addressed element, subsequent elements are then accessed with a negative offset from that address, and GDB is not currently happy with this configuration. The changes here can be summarised as, stop treating signed values as unsigned, specifically, the array stride, and offsets calculated using the array stride. This issue was identified on the mailing list by Sergio: https://sourceware.org/ml/gdb-patches/2020-01/msg00360.html The test for this issue is a new one written by me as the copyright status of the original test is currently unknown. gdb/ChangeLog: * gdbtypes.c (create_array_type_with_stride): Handle negative array strides. * valarith.c (value_subscripted_rvalue): Likewise. gdb/testsuite/ChangeLog: * gdb.fortran/derived-type-striding.exp: Add a new test. * gdb.fortran/derived-type-striding.f90: Add pointer variable for new test. --- gdb/valarith.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'gdb/valarith.c') diff --git a/gdb/valarith.c b/gdb/valarith.c index 79b1486..be0e073 100644 --- a/gdb/valarith.c +++ b/gdb/valarith.c @@ -187,7 +187,7 @@ value_subscripted_rvalue (struct value *array, LONGEST index, LONGEST lowerbound { struct type *array_type = check_typedef (value_type (array)); struct type *elt_type = check_typedef (TYPE_TARGET_TYPE (array_type)); - ULONGEST elt_size = type_length_units (elt_type); + LONGEST elt_size = type_length_units (elt_type); /* Fetch the bit stride and convert it to a byte stride, assuming 8 bits in a byte. */ @@ -199,7 +199,7 @@ value_subscripted_rvalue (struct value *array, LONGEST index, LONGEST lowerbound elt_size = stride / (unit_size * 8); } - ULONGEST elt_offs = elt_size * (index - lowerbound); + LONGEST elt_offs = elt_size * (index - lowerbound); if (index < lowerbound || (!TYPE_ARRAY_UPPER_BOUND_IS_UNDEFINED (array_type) -- cgit v1.1