Add comment in dwarf2read.c::read_subrange_type

This comment explains why we sometimes sign-extend the range type
bounds when we normally shouldn't have to.

gdb/ChangeLog:

        * dwarf2read.c (read_subrange_type): Add comment.
This commit is contained in:
Joel Brobecker 2014-02-26 10:53:05 -08:00
parent 55426c9d52
commit dbb9c2b1f2
2 changed files with 11 additions and 0 deletions

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@ -1,3 +1,7 @@
2014-02-27 Joel Brobecker <brobecker@adacore.com>
* dwarf2read.c (read_subrange_type): Add comment.
2014-02-27 Joel Brobecker <brobecker@adacore.com>
* dwarf2read.c (update_enumeration_type_from_children): New

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@ -14522,6 +14522,13 @@ read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
}
}
/* Normally, the DWARF producers are expected to use a signed
constant form (Eg. DW_FORM_sdata) to express negative bounds.
But this is unfortunately not always the case, as witnessed
with GCC, for instance, where the ambiguous DW_FORM_dataN form
is used instead. To work around that ambiguity, we treat
the bounds as signed, and thus sign-extend their values, when
the base type is signed. */
negative_mask =
(LONGEST) -1 << (TYPE_LENGTH (base_type) * TARGET_CHAR_BIT - 1);
if (!TYPE_UNSIGNED (base_type) && (low & negative_mask))