From: Simon Marchi <simon.marchi@efficios.com>
To: gdb-patches@sourceware.org
Cc: Simon Marchi <simon.marchi@efficios.com>
Subject: [PATCH 1/2] gdb/testsuite: add test for negative subrange bounds with unsigned form
Date: Fri, 20 Jan 2023 00:08:23 -0500 [thread overview]
Message-ID: <20230120050824.306976-1-simon.marchi@efficios.com> (raw)
I am looking at this code [1]:
/* 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 =
-((ULONGEST) 1 << (base_type->length () * TARGET_CHAR_BIT - 1));
if (low.kind () == PROP_CONST
&& !base_type->is_unsigned () && (low.const_val () & negative_mask))
low.set_const_val (low.const_val () | negative_mask);
if (high.kind () == PROP_CONST
&& !base_type->is_unsigned () && (high.const_val () & negative_mask))
high.set_const_val (high.const_val () | negative_mask);
Nothing in the testsuite seems to exercise it, as when I remove it, all
of gdb.dwarf2 still passes. And tests in other directories would be
compiler-dependent, so would rely on having a buggy compiler.
Update gdb.dwarf2/subrange.exp to have a test for it. When removing the
code above, the new test fails with:
ptype array_with_buggy_negative_bounds_type^M
type = array [240..244] of signed_byte^M
(gdb) FAIL: gdb.dwarf2/subrange.exp: ptype array_with_buggy_negative_bounds_type
instead of the expected:
ptype array_with_buggy_negative_bounds_type^M
type = array [-16..-12] of signed_byte^M
(gdb) PASS: gdb.dwarf2/subrange.exp: ptype array_with_buggy_negative_bounds_type
[1] https://gitlab.com/gnutools/binutils-gdb/-/blob/5ea14aa4e53fa37f4ba4517497ed2c1e4c60dee2/gdb/dwarf2/read.c#L17681-17695
Change-Id: I1992a3ff0cb1e90fa8a9114dae6c591792f059c2
---
gdb/testsuite/gdb.dwarf2/subrange.exp | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/gdb/testsuite/gdb.dwarf2/subrange.exp b/gdb/testsuite/gdb.dwarf2/subrange.exp
index 72d7babc88e..8a8443f31a8 100644
--- a/gdb/testsuite/gdb.dwarf2/subrange.exp
+++ b/gdb/testsuite/gdb.dwarf2/subrange.exp
@@ -28,6 +28,7 @@ Dwarf::assemble $asm_file {
compile_unit {{language @DW_LANG_Pascal83}} {
declare_labels byte_label typedef_label array_label
+ # A subrange's underlying type that is a typedef.
byte_label: base_type {
{name byte}
{encoding @DW_ATE_unsigned}
@@ -54,6 +55,28 @@ Dwarf::assemble $asm_file {
{name TByteArray}
{type :$array_label}
}
+
+ # This subrange's underlying type is signed, but the bounds are
+ # specified using a non-signed form.
+ declare_labels signed_byte_label subrange_with_buggy_negative_bounds_label
+
+ signed_byte_label: base_type {
+ {name signed_byte}
+ {encoding @DW_ATE_signed}
+ {byte_size 1 DW_FORM_sdata}
+ }
+
+ # The bounds mean -16 to -12.
+ subrange_with_buggy_negative_bounds_label: subrange_type {
+ {lower_bound 0xf0 DW_FORM_udata}
+ {upper_bound 0xf4 DW_FORM_udata}
+ {type :$signed_byte_label}
+ }
+
+ DW_TAG_variable {
+ {name subrange_with_buggy_negative_bounds_variable}
+ {type :$subrange_with_buggy_negative_bounds_label}
+ }
}
}
}
@@ -67,3 +90,5 @@ gdb_test_no_output "set language pascal"
gdb_test "ptype TByteArray" \
"type = array \\\[0\\.\\.191\\\] of byte"
+gdb_test "ptype subrange_with_buggy_negative_bounds_variable" \
+ "type = -16..-12"
--
2.39.1
next reply other threads:[~2023-01-20 5:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-20 5:08 Simon Marchi [this message]
2023-01-20 5:08 ` [PATCH 2/2] gdb/dwarf: fix UBsan crash in read_subrange_type Simon Marchi
2023-01-20 13:03 ` Andrew Burgess
2023-01-20 16:51 ` Simon Marchi
2023-01-20 12:51 ` [PATCH 1/2] gdb/testsuite: add test for negative subrange bounds with unsigned form Andrew Burgess
2023-01-20 16:38 ` Simon Marchi
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