On Tue, Oct 23, 2018 at 10:59 AM Martin Liška <[email protected]> wrote:
>
> Hi.
>
> I've returned to this long-lasting issue after quite some time. Thanks to
> Honza I hope
> I can now address the root cause which caused output of a string constant
> when debug info
> was emitted. The problematic situation happened with following back-trace:
>
> #0 mergeable_string_section (decl=<string_cst 0x7ffff67be210>, align=64,
> flags=0) at /home/marxin/Programming/gcc/gcc/varasm.c:808
> #1 0x0000000001779bf3 in default_elf_select_section (decl=<string_cst
> 0x7ffff67be210>, reloc=0, align=64) at
> /home/marxin/Programming/gcc/gcc/varasm.c:6739
> #2 0x000000000176efb6 in get_constant_section (exp=<string_cst
> 0x7ffff67be210>, align=64) at /home/marxin/Programming/gcc/gcc/varasm.c:3302
> #3 0x000000000176f468 in build_constant_desc (exp=<string_cst
> 0x7ffff67be210>) at /home/marxin/Programming/gcc/gcc/varasm.c:3371
> #4 0x000000000176f81c in output_constant_def (exp=<string_cst
> 0x7ffff67be210>, defer=1) at /home/marxin/Programming/gcc/gcc/varasm.c:3434
> #5 0x000000000176d406 in decode_addr_const (exp=<addr_expr 0x7ffff682f8c0>,
> value=0x7fffffffc540) at /home/marxin/Programming/gcc/gcc/varasm.c:2951
> #6 0x000000000176d93f in const_hash_1 (exp=<addr_expr 0x7ffff682f8c0>) at
> /home/marxin/Programming/gcc/gcc/varasm.c:3054
> #7 0x000000000176fdc2 in lookup_constant_def (exp=<addr_expr
> 0x7ffff682f8c0>) at /home/marxin/Programming/gcc/gcc/varasm.c:3557
> #8 0x0000000000dd5778 in cst_pool_loc_descr (loc=<addr_expr 0x7ffff682f8c0>)
> at /home/marxin/Programming/gcc/gcc/dwarf2out.c:17288
>
> That was in situation where we emit debug info of a function that has an
> inlined __PRETTY_FUNCTION__ from
> a different function. As seen, the constant is output due to const_hash_1
> function call. Proper fix would
> be to not emit these string constants for purpose of hash function.
possibly sth like the following - that avoids all cases of calling
output_constant_def. Probably worth testing
separately.
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 91650eea9f7..9121dbd2c84 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -3047,6 +3047,10 @@ const_hash_1 (const tree exp)
}
case ADDR_EXPR:
+ if (CONSTANT_CLASS_P (TREE_OPERAND (exp, 0)))
+ return const_hash_1 (TREE_OPERAND (exp, 0));
+
+ /* Fallthru. */
case FDESC_EXPR:
{
struct addr_const value;
> However, I still see some minor ICEs, it's probably related to
> decay_conversion in cp_fname_init:
>
> 1) ./xg++ -B.
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-__func__2.C
>
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-__func__2.C:6:17:
> internal compiler error: Segmentation fault
> 6 | [] { return __func__; }();
> | ^~~~~~~~
> 0x1344568 crash_signal
> /home/marxin/Programming/gcc/gcc/toplev.c:325
> 0x7ffff6bc310f ???
>
> /usr/src/debug/glibc-2.27-6.1.x86_64/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
> 0x9db134 is_capture_proxy(tree_node*)
> /home/marxin/Programming/gcc/gcc/cp/lambda.c:261
> 0xaeecb7 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
> /home/marxin/Programming/gcc/gcc/cp/pt.c:16700
> 0xaee5fd tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
> /home/marxin/Programming/gcc/gcc/cp/pt.c:16636
> 0xaf0ffb tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
> /home/marxin/Programming/gcc/gcc/cp/pt.c:16942
>
> where
> (gdb) p debug_tree(decl)
> <var_decl 0x7ffff7fee480 __func__
> type <pointer_type 0x7ffff69b5540
> type <integer_type 0x7ffff69b5498 char readonly unsigned string-flag
> type_6 QI
> size <integer_cst 0x7ffff698df78 constant 8>
> unit-size <integer_cst 0x7ffff698df90 constant 1>
> align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> 0x7ffff69b5498 precision:8 min <integer_cst 0x7ffff698dfd8 0> max
> <integer_cst 0x7ffff698dfc0 255>
> pointer_to_this <pointer_type 0x7ffff69b5540>>
> unsigned DI
> size <integer_cst 0x7ffff698de88 constant 64>
> unit-size <integer_cst 0x7ffff698dea0 constant 8>
> align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> 0x7ffff69b5540>
> readonly used tree_2 unsigned DI
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-__func__2.C:6:17
> size <integer_cst 0x7ffff698de88 64> unit-size <integer_cst 0x7ffff698dea0 8>
> align:64 warn_if_not_align:0 context <function_decl 0x7ffff67abd00
> operator()>
> value-expr <nop_expr 0x7ffff67b7660 type <pointer_type 0x7ffff69b5540>
> constant
> arg:0 <addr_expr 0x7ffff67b7640 type <pointer_type 0x7ffff67bd3f0>
> constant
> arg:0 <string_cst 0x7ffff67b7620 type <array_type 0x7ffff67bd348>
> constant "operator()\000">>>>
>
> and
> #0 0x00000000009db134 in is_capture_proxy (decl=<tree 0x0>) at
> /home/marxin/Programming/gcc/gcc/cp/lambda.c:261
>
> 2 ) ./xg++ -B.
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pretty2.C -c
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pretty2.C:16:24:
> internal compiler error: Segmentation fault
> 16 | __PRETTY_FUNCTION__), 0))
> | ^
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pretty2.C:36:10: note:
> in expansion of macro ‘assert’
> 36 | int a = (assert (foo ()), 1);
> | ^~~~~~
> 0x1344568 crash_signal
> /home/marxin/Programming/gcc/gcc/toplev.c:325
> 0x7ffff6bc310f ???
>
> /usr/src/debug/glibc-2.27-6.1.x86_64/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
> 0x9db270 is_capture_proxy(tree_node*)
> /home/marxin/Programming/gcc/gcc/cp/lambda.c:265
> 0x9dbad9 is_normal_capture_proxy(tree_node*)
> /home/marxin/Programming/gcc/gcc/cp/lambda.c:274
> 0x9c1fe6 mark_use(tree_node*, bool, bool, unsigned int, bool)
> /home/marxin/Programming/gcc/gcc/cp/expr.c:114
> 0x89d9ab convert_like_real
> /home/marxin/Programming/gcc/gcc/cp/call.c:6905
>
> where:
>
> (gdb) p debug_tree(decl)
> <var_decl 0x7ffff7fee870 __PRETTY_FUNCTION__
> type <pointer_type 0x7ffff69b4540
> type <integer_type 0x7ffff69b4498 char readonly unsigned string-flag
> type_6 QI
> size <integer_cst 0x7ffff698df78 constant 8>
> unit-size <integer_cst 0x7ffff698df90 constant 1>
> align:8 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> 0x7ffff69b4498 precision:8 min <integer_cst 0x7ffff698dfd8 0> max
> <integer_cst 0x7ffff698dfc0 255>
> pointer_to_this <pointer_type 0x7ffff69b4540>>
> unsigned type_6 DI
> size <integer_cst 0x7ffff698de88 constant 64>
> unit-size <integer_cst 0x7ffff698dea0 constant 8>
> align:64 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> 0x7ffff69b4540>
> readonly used tree_1 tree_2 unsigned read decl_6 DI
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/ext/pretty2.C:36:10 size
> <integer_cst 0x7ffff698de88 64> unit-size <integer_cst 0x7ffff698dea0 8>
> align:64 warn_if_not_align:0
> value-expr <nop_expr 0x7ffff67b69a0 type <pointer_type 0x7ffff69b4540>
> constant
> arg:0 <addr_expr 0x7ffff67b6980 type <pointer_type 0x7ffff67c3738>
> constant
> arg:0 <string_cst 0x7ffff67b6960 type <array_type 0x7ffff67c3690>
> constant "top level\000">>> chain <var_decl 0x7ffff7fee7e0 a>>
>
> Can please a C++ maintainer help me with that? Having that I hope I can
> finish the patch.
>
> Thank you,
> Martin
