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Fix crash with DW_FORM_implicit_const

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Jakub pointed out that using DW_FORM_implicit_const with
DW_AT_bit_size would cause gdb to crash.  This happened because
DW_FORM_implicit_const is not an "unsigned" form, causing as_unsigned
to assert.  This patch fixes the problem.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30651
Approved-By: Andrew Burgess <aburgess@redhat.com>
This commit is contained in:
Tom Tromey
2023-07-20 15:48:46 -06:00
parent e8fc65713d
commit 4d051f3a4e
3 changed files with 22 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
gdb/dwarf2/read.c
+17 -12
View File
@@ -15420,20 +15420,25 @@ read_base_type (struct die_info *die, struct dwarf2_cu *cu)
if (TYPE_SPECIFIC_FIELD (type) == TYPE_SPECIFIC_INT)
{
attr = dwarf2_attr (die, DW_AT_bit_size, cu);
if (attr != nullptr && attr->as_unsigned () <= 8 * type->length ())
if (attr != nullptr && attr->form_is_constant ())
{
unsigned real_bit_size = attr->as_unsigned ();
attr = dwarf2_attr (die, DW_AT_data_bit_offset, cu);
/* Only use the attributes if they make sense together. */
if (attr == nullptr
|| (attr->as_unsigned () + real_bit_size
<= 8 * type->length ()))
unsigned real_bit_size = attr->constant_value (0);
if (real_bit_size >= 0 && real_bit_size <= 8 * type->length ())
{
TYPE_MAIN_TYPE (type)->type_specific.int_stuff.bit_size
= real_bit_size;
if (attr != nullptr)
TYPE_MAIN_TYPE (type)->type_specific.int_stuff.bit_offset
= attr->as_unsigned ();
attr = dwarf2_attr (die, DW_AT_data_bit_offset, cu);
/* Only use the attributes if they make sense together. */
if (attr == nullptr
|| (attr->form_is_constant ()
&& attr->constant_value (0) >= 0
&& (attr->constant_value (0) + real_bit_size
<= 8 * type->length ())))
{
TYPE_MAIN_TYPE (type)->type_specific.int_stuff.bit_size
= real_bit_size;
if (attr != nullptr)
TYPE_MAIN_TYPE (type)->type_specific.int_stuff.bit_offset
= attr->constant_value (0);
}
}
}
}
gdb/testsuite/gdb.dwarf2/intbits.exp
+1 -1
View File
@@ -43,7 +43,7 @@ Dwarf::assemble ${asm_file} {
{DW_AT_endianity @DW_END_little}
{DW_AT_name "i7"}
{DW_AT_byte_size 2 DW_FORM_udata}
{DW_AT_bit_size 7 DW_FORM_udata}
{DW_AT_bit_size 7 DW_FORM_implicit_const}
}
DW_TAG_variable {
gdb/testsuite/lib/dwarf.exp
+4
View File
@@ -693,6 +693,7 @@ namespace eval Dwarf {
_op .ascii [_quote $value]
}
DW_FORM_implicit_const -
DW_FORM_flag_present {
# We don't need to emit anything.
}
@@ -917,6 +918,9 @@ namespace eval Dwarf {
}
_op .uleb128 $_constants($attr_name) $attr_name
_op .uleb128 $_constants($attr_form) $attr_form_comment
if {$attr_form eq "DW_FORM_implicit_const"} {
_op .sleb128 $attr_value "the constant"
}
}
}