gdb will assert when printing "container_object2" in the attached sample. value.c:828: internal-error: int value_contents_bits_eq(const value*, int, const value*, int, int): Assertion `offset1 + length <= TYPE_LENGTH (val1->enclosing_type) * TARGET_CHAR_BIT' failed. The use of a typedef in the declaration of one of the fields of the struct container_struct2 is triggering the issue. In the attached sample, there are two nearly identical structs, container_struct1 and container_struct2. The only difference between the two is the use of a typedef in container_struct2 when declaring one of the fields. The field (_vla_struct_object2) is a variable length struct. To reproduce: > gcc -g vls_assert.c > gdb a.out (gdb) b 49 Breakpoint 1 at 0x40095a: file vls_assert.c, line 49. (gdb) r Breakpoint 1, vls_factory (n=5) at vls_assert.c:50 50 return; (gdb) p container_object1 $1 = {_container_member1 = 5, _vla_struct_object1 = {_some_member = 10, _vla_field = {0, 2, 4, 6, 8}}} (gdb) p container_object2 $2 = {_container_member2 = 15, _vla_struct_object2 = {_some_member = 0, _vla_field = { value.c:828: internal-error: int value_contents_bits_eq(const value*, int, const value*, int, int): Assertion `offset1 + length <= TYPE_LENGTH (val1->enclosing_type) * TARGET_CHAR_BIT' failed. I reproduced the issue with gcc 4.8.3 and gcc 6.3.0 on EL7.0.
Created attachment 9974 [details] assertion reproducer
From: Keith Seitz <keiths@redhat.com> [PATCH] Compute proper length for dynamic types of TYPE_CODE_TYPEDEF https://sourceware.org/ml/gdb-patches/2017-06/msg00679.html Message-Id: <1498265971-27536-1-git-send-email-keiths@redhat.com>
submitted updated patch: https://sourceware.org/pipermail/gdb-patches/2020-June/169359.html
The master branch has been updated by Tom de Vries <vries@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2f33032a93f24ccc0c0d2f23e2a3ec0442f638d4 commit 2f33032a93f24ccc0c0d2f23e2a3ec0442f638d4 Author: Keith Seitz <keiths@redhat.com> Date: Thu Jun 11 14:34:44 2020 +0200 Compute proper length for dynamic types of TYPE_CODE_TYPEDEF This patch fixes gdb/21356 in which we hit an assertion in value_contents_bits_eq: (gdb) p container_object2 (gdb) p container_object2 $1 = {_container_member2 = 15, _vla_struct_object2 = {_some_member = 0, _vla_field = { ../../src/gdb/value.c:829: internal-error: \ int value_contents_bits_eq(const value*, int, const value*, int, int): \ Assertion `offset1 + length \ <= TYPE_LENGTH (val1->enclosing_type) * TARGET_CHAR_BIT' failed. This is happening because TYPE_LENGTH (val1->enclosing_type) is erroneously based on enclosing_type, which is a typedef, instead of the actual underlying type. This can be traced back to resolve_dynamic_struct, where the size of the type is computed: ... TYPE_FIELD_TYPE (resolved_type, i) = resolve_dynamic_type_internal (TYPE_FIELD_TYPE (resolved_type, i), &pinfo, 0); gdb_assert (TYPE_FIELD_LOC_KIND (resolved_type, i) == FIELD_LOC_KIND_BITPOS); new_bit_length = TYPE_FIELD_BITPOS (resolved_type, i); if (TYPE_FIELD_BITSIZE (resolved_type, i) != 0) new_bit_length += TYPE_FIELD_BITSIZE (resolved_type, i); else new_bit_length += (TYPE_LENGTH (TYPE_FIELD_TYPE (resolved_type, i)) * TARGET_CHAR_BIT); ... In this function, resolved_type is TYPE_CODE_TYPEDEF which is not what we want to use to calculate the size of the actual field. This patch fixes this and the similar problem in resolve_dynamic_union. gdb/ChangeLog: 2020-06-11 Keith Seitz <keiths@redhat.com> PR gdb/21356 * gdbtypes.c (resolve_dynamic_union, resolve_dynamic_struct): Resolve typedefs for type length calculations. gdb/testsuite/ChangeLog: 2020-06-11 Keith Seitz <keiths@redhat.com> PR gdb/21356 * gdb.base/vla-datatypes.c (vla_factory): Add typedef for struct vla_struct. Add new struct vla_typedef and union vla_typedef_union and corresponding instantiation objects. Initialize new objects. * gdb.base/vla-datatypes.exp: Add tests for vla_typedef_struct_object and vla_typedef_union_object. Fixup type for vla_struct_object.
Patch with fix and test-case addition committed, marking resolved-fixed.