[patch] compile: Fix crash on cv-qualified self-reference

Jan Kratochvil
2015-04-18T17:28:51Z

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Hi,

with this modified testcase GDB would:

compile code struct_object.selffield = &struct_object
./compile/compile-c-types.c:83: internal-error: insert_type: Assertion `add == NULL || add->gcc_type == gcc_type' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) FAIL: gdb.compile/compile.exp: compile code struct_object.selffield = &struct_object (GDB internal error)

While the insert_type() assertion looks unclear trying to fix it one ends up
with either GCC crash
[gcc libcc1] build_qualified_type for self-referencing/incomplete types
https://gcc.gnu.org/ml/gcc/2015-04/msg00108.html
c_incomplete_type_error()
or after fixing up the GCC type for proper error reporting one gets:
gdb command line:1:1: error: invalid use of incomplete typedef ‘sv’
which is the real culprit of this bug as explained in this patch.

This patch is related to the XFAIL introduced by
[PATCH v3 5/9] compile: Use -Wall, not -w
https://sourceware.org/ml/gdb-patches/2015-04/msg00429.html
as for proper -Wall happiness the 'volatile' qualifier needs to be added there
- but adding the qualifier has caused this crash.

No regressions on {x86_64,x86_64-m32,i686}-fedora23pre-linux-gnu.

Thanks,
Jan

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gdb/ChangeLog
2015-04-18 Jan Kratochvil <jan.kratochvil@redhat.com>

compile: Fix crash on cv-qualified self-reference.
* compile/compile-c-types.c (convert_struct_or_union): Apply
build_qualified_type.
(convert_type_basic): Do not apply build_qualified_type for
TYPE_CODE_STRUCT and TYPE_CODE_UNION.

gdb/testsuite/ChangeLog
2015-04-18 Jan Kratochvil <jan.kratochvil@redhat.com>

compile: Fix crash on cv-qualified self-reference.
* gdb.compile/compile.c (struct struct_type): Add volatile for
selffield.

diff --git a/gdb/compile/compile-c-types.c b/gdb/compile/compile-c-types.c
index 2b521bc..420f61d 100644
--- a/gdb/compile/compile-c-types.c
+++ b/gdb/compile/compile-c-types.c
@@ -166,9 +166,13 @@ convert_struct_or_union (struct compile_c_instance *context, struct type *type)
{
int i;
gcc_type result;
+ int quals;

/* First we create the resulting type and enter it into our hash
- table. This lets recursive types work. */
+ table. This lets recursive types work. We have to create gcc_type
+ already with its qualifiers to prevent recursively calling
+ build_qualified_type for unfinished TYPE as build_qualified_type
+ creates a copy of the type, remaining unfinished forever. */
if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
result = C_CTX (context)->c_ops->build_record_type (C_CTX (context));
else
@@ -176,6 +180,15 @@ convert_struct_or_union (struct compile_c_instance *context, struct type *type)
gdb_assert (TYPE_CODE (type) == TYPE_CODE_UNION);
result = C_CTX (context)->c_ops->build_union_type (C_CTX (context));
}
+ quals = 0;
+ if (TYPE_CONST (type))
+ quals |= GCC_QUALIFIER_CONST;
+ if (TYPE_VOLATILE (type))
+ quals |= GCC_QUALIFIER_VOLATILE;
+ if (TYPE_RESTRICT (type))
+ quals |= GCC_QUALIFIER_RESTRICT;
+ result = C_CTX (context)->c_ops->build_qualified_type (C_CTX (context),
+ result, quals);
insert_type (context, type, result);

for (i = 0; i < TYPE_NFIELDS (type); ++i)
@@ -329,10 +342,13 @@ static gcc_type
convert_type_basic (struct compile_c_instance *context, struct type *type)
{
/* If we are converting a qualified type, first convert the
- unqualified type and then apply the qualifiers. */
+ unqualified type and then apply the qualifiers, except for the
+ types handling qualifiers on their own. */
if ((TYPE_INSTANCE_FLAGS (type) & (TYPE_INSTANCE_FLAG_CONST
| TYPE_INSTANCE_FLAG_VOLATILE
- | TYPE_INSTANCE_FLAG_RESTRICT)) != 0)
+ | TYPE_INSTANCE_FLAG_RESTRICT)) != 0
+ && (TYPE_CODE (type) != TYPE_CODE_STRUCT
+ && TYPE_CODE (type) != TYPE_CODE_UNION))
return convert_qualified (context, type);

switch (TYPE_CODE (type))
diff --git a/gdb/testsuite/gdb.compile/compile.c b/gdb/testsuite/gdb.compile/compile.c
index 3d5f20a..41ff087 100644
--- a/gdb/testsuite/gdb.compile/compile.c
+++ b/gdb/testsuite/gdb.compile/compile.c
@@ -42,7 +42,7 @@ struct struct_type {
float floatfield;
double doublefield;
const union union_type *ptrfield;
- struct struct_type *selffield;
+ volatile struct struct_type *selffield;
int arrayfield[5];
_Complex double complexfield;
_Bool boolfield;