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cac6b1f3b0
Consider the following test-case:
...
$ cat a.h
namespace ns {
class A {
public:
enum {
val1 = 1
};
};
}
$ cat main.c
ns::A a;
int
main (void)
{
return 0;
}
$ cat val1.c
int u1 = ns::A::val1;
...
compiled with debug info:
...
$ g++ main.c val1.c -g
...
When trying to print ns::A::val with current trunk and gdb 15.1 we get:
...
$ gdb -q -batch a.out -ex "print ns::A::val1"
There is no field named val1
...
This PR c++/31900.
With gdb 14.2 we get the expected:
...
$ gdb -q -batch a.out -ex "print ns::A::val1"
$1 = ns::A::val1
...
This is a regression since commit 4e417d7bb1 ("Change handling of
DW_TAG_enumeration_type in DWARF scanner").
Reverting the commit on current trunk fixes the problem.
So how does this problem happen?
First, let's consider the current trunk, with the commit reverted.
Gdb looks for the entry ns::A::val1, and find this entry:
...
[29] ((cooked_index_entry *) 0x7f7830002ef0)
name: val1
canonical: val1
qualified: ns::A::val1
DWARF tag: DW_TAG_enumerator
flags: 0x0 []
DIE offset: 0x15a
parent: ((cooked_index_entry *) 0x7f7830002ec0) [A]
...
and expands the corresponding CU val1.c containing this debug info:
...
<2><14a>: Abbrev Number: 3 (DW_TAG_class_type)
<14b> DW_AT_name : A
<14d> DW_AT_byte_size : 1
<3><150>: Abbrev Number: 4 (DW_TAG_enumeration_type)
<151> DW_AT_encoding : 7 (unsigned)
<152> DW_AT_byte_size : 4
<153> DW_AT_type : <0x163>
<159> DW_AT_accessibility: 1 (public)
<4><15a>: Abbrev Number: 5 (DW_TAG_enumerator)
<15b> DW_AT_name : val1
<15f> DW_AT_const_value : 1
<4><160>: Abbrev Number: 0
<3><161>: Abbrev Number: 0
<2><162>: Abbrev Number: 0
...
after which it finds ns::A::val1 in the expanded symtabs.
Now let's consider the current trunk as is (so, with the commit present).
Gdb looks for the entry ns::A::val1, but doesn't find it because the val1
entry is missing its parent:
...
[29] ((cooked_index_entry *) 0x7f5240002ef0)
name: val1
canonical: val1
qualified: val1
DWARF tag: DW_TAG_enumerator
flags: 0x0 []
DIE offset: 0x15a
parent: ((cooked_index_entry *) 0)
...
Then gdb looks for the entry ns::A, and finds this entry:
...
[3] ((cooked_index_entry *) 0x7f5248002ec0)
name: A
canonical: A
qualified: ns::A
DWARF tag: DW_TAG_class_type
flags: 0x0 []
DIE offset: 0xdd
parent: ((cooked_index_entry *) 0x7f5248002e90) [ns]
...
which corresponds to this debug info, which doesn't contain val1
due to -fno-eliminate-unused-debug-types:
...
<2><dd>: Abbrev Number: 3 (DW_TAG_class_type)
<de> DW_AT_name : A
<e0> DW_AT_byte_size : 1
<2><e3>: Abbrev Number: 0
...
Gdb expands the corresponding CU main.c, after which it doesn't find
ns::A::val1 in the expanded symtabs.
The root cause of the problem is the missing parent on the val1
cooked_index_entry, but this only becomes user-visible through the
elaborate scenario above.
Add a test-case gdb.dwarf2/enum-type-c++.exp that contains a regression test
for this problem that doesn't rely on expansion state or
-feliminate-unused-debug-types, but simply tests for the root cause by
grepping for ns::A::val1 in the output of "maint print objfile".
Tested on x86_64-linux.
Approved-By: Tom Tromey <tom@tromey.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31900
(cherry picked from commit 2693187cc5)
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