Created attachment 14984 [details] bitint-39a.s gdb 12.1 (haven't tried more recent) crashes with ../../gdb/dwarf2/attribute.h:90: internal-error: as_unsigned: Assertion `form_is_unsigned ()' failed. A problem internal to GDB has been detected, further debugging may prove unreliable. when trying to debug following testcase: int v; __attribute__((noinline, noclone)) void bar (void) { v++; } __attribute__((noinline, noclone)) signed _BitInt (19) t111_1mul (unsigned _BitInt (19) x, signed _BitInt (19) y) { signed _BitInt (19) r; if (__builtin_mul_overflow (x, y, &r)) bar (); return r; } __attribute__((noinline, noclone)) signed _BitInt (19) t111_2mul (signed _BitInt (19) y) { unsigned _BitInt (19) x = (2); signed _BitInt (19) r; if (__builtin_mul_overflow (x, y, &r)) bar (); return r; } __attribute__((noinline, noclone)) signed _BitInt (19) t111_3mul (signed _BitInt (19) y) { signed _BitInt (19) r; if (__builtin_mul_overflow ((unsigned _BitInt (19)) (2), y, &r)) bar (); return r; } __attribute__((noinline, noclone)) signed _BitInt (19) t111_4mul (unsigned _BitInt (19) x) { signed _BitInt (19) y = (-262143wb - 1 / 2); signed _BitInt (19) r; if (__builtin_mul_overflow (x, y, &r)) bar (); return r; } __attribute__((noinline, noclone)) signed _BitInt (19) t111_5mul (unsigned _BitInt (19) x) { signed _BitInt (19) r; if (__builtin_mul_overflow (x, (signed _BitInt (19)) (-262143wb - 1 / 2), &r)) bar (); return r; } __attribute__((noinline, noclone)) void t111mul (void) { unsigned _BitInt (19) x = (2); signed _BitInt (19) y = (-262143wb - 1 / 2); signed _BitInt (19) r1, r2; v = 0; if (t111_1mul (x, y) != (signed _BitInt (19)) (-262143wb - 1) || t111_2mul (y) != (signed _BitInt (19)) (-262143wb - 1) || t111_3mul (y) != (signed _BitInt (19)) (-262143wb - 1) || t111_4mul (x) != (signed _BitInt (19)) (-262143wb - 1) || t111_5mul (x) != (signed _BitInt (19)) (-262143wb - 1)) __builtin_abort (); if (__builtin_mul_overflow (x, y, &r1)) bar (); if (r1 != (signed _BitInt (19)) (-262143wb - 1)) __builtin_abort (); if (__builtin_mul_overflow ((unsigned _BitInt (19)) (2), (signed _BitInt (19)) (-262143wb - 1 / 2), &r2)) bar (); if (r2 != (signed _BitInt (19)) (-262143wb - 1) || v != 7 * 0) __builtin_abort (); } int main () { t111mul (); return 0; } with GCC trunk patched with https://gcc.gnu.org/bugzilla/attachment.cgi?id=55572&action=diff compiled with -g -std=gnu2x. The DW_TAG_base_type for _BitInt uses .byte 0x4 # uleb128 0x4; (abbrev code) .byte 0x24 # uleb128 0x24; (TAG: DW_TAG_base_type) .byte 0 # DW_children_no .byte 0xb # uleb128 0xb; (DW_AT_byte_size) .byte 0x21 # uleb128 0x21; (DW_FORM_implicit_const) .byte 0x4 # sleb128 4 .byte 0x3e # uleb128 0x3e; (DW_AT_encoding) .byte 0xb # uleb128 0xb; (DW_FORM_data1) .byte 0xd # uleb128 0xd; (DW_AT_bit_size) .byte 0x21 # uleb128 0x21; (DW_FORM_implicit_const) .byte 0x13 # sleb128 19 .byte 0x3 # uleb128 0x3; (DW_AT_name) .byte 0xe # uleb128 0xe; (DW_FORM_strp) .byte 0 .byte 0 but I don't see anything wrong on that, DW_FORM_implicit_const always uses sleb128 encoding of the constant and all that matters is whether that constant is signed or unsigned, not that it uses sleb128 encoding. The crash is after run up
Created attachment 14985 [details] bitint-39a.c
I have a fix, just have to write a test case.
There should probably be a separate bug for implementing this stuff in gdb's parser / expression evaluator.
Yeah. I've filed https://dwarfstd.org/issues/230529.1.html proposal for DWARF6, but it hasn't been discussed yet. And, while GDB can print some _BitInt values just fine (seems if they are multiple of 64 bits, it gives up on others. Right now when debugging stuff I'm just printing the limbs using x/<N>gx &var when GDB can't handle it.
https://sourceware.org/pipermail/gdb-patches/2023-July/201040.html
(In reply to Jakub Jelinek from comment #4) > Yeah. I've filed https://dwarfstd.org/issues/230529.1.html proposal for > DWARF6, but it hasn't been discussed yet. And, while GDB can print some > _BitInt values just fine (seems if they are multiple of 64 bits, it gives up > on others. Right now when debugging stuff I'm just printing the limbs using > x/<N>gx &var when GDB can't handle it. It looks like there are new suffixes too? And the semantics of these aren't identical to existing int types? And I guess new ABI... probably will end up wanting several gdb bugs to implement it all.
The master branch has been updated by Tom Tromey <tromey@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4d051f3a4e2839225f7de0ea783e2fdca1c7717e commit 4d051f3a4e2839225f7de0ea783e2fdca1c7717e Author: Tom Tromey <tom@tromey.com> Date: Thu Jul 20 15:48:46 2023 -0600 Fix crash with DW_FORM_implicit_const 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>
Fixed.