https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127463
Bug ID: 127463
Summary: internal compiler error: in merge_weak
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: 0599jiangyc at gmail dot com
Target Milestone: ---
The following code:
```cpp
void * foo (void) { return (void *)foo; }
extern void * foo (void) __attribute__((weak));
```
Resulted in this output:
```
/tmp/test.cc:18:1: error: expected initializer before 'extern'
18 | extern void * foo (void);
| ^~~~~~
/tmp/test.cc:21:46: internal compiler error: in merge_weak, at varasm.cc:6268
21 | extern void * foo (void) __attribute__((weak));
| ^
0x3046dcb internal_error(char const*, ...)
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/diagnostic-global-context.cc:787
0xdd9a1e fancy_abort(char const*, int, char const*)
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/diagnostics/context.cc:1813
0xa7eb2a merge_weak(tree_node*, tree_node*)
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/varasm.cc:6268
0xeb8cf0 duplicate_decls(tree_node*, tree_node*, bool, bool)
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/decl.cc:3047
0xfaabcf pushdecl(tree_node*, bool)
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/name-lookup.cc:4089
0xed26dd start_decl(cp_declarator const*, cp_decl_specifier_seq*, int,
tree_node*, tree_node*, tree_node**)
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/decl.cc:6822
0x10105fa cp_parser_init_declarator
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/parser.cc:26383
0x10125cb cp_parser_simple_declaration
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/parser.cc:18207
0x10221cf cp_parser_declaration
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/parser.cc:17744
0x1024c33 cp_parser_toplevel_declaration
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/parser.cc:17848
0x1024c33 cp_parser_translation_unit
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/parser.cc:5610
0x1024c33 c_parse_file()
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/cp/parser.cc:57910
0x11b8619 c_common_parse_file()
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-src/gcc/c-family/c-opts.cc:1437
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-install/libexec/gcc/x86_64-pc-linux-gnu/17.0.0/cc1plus
-quiet -imultiarch x86_64-linux-gnu -D_GNU_SOURCE /tmp/test.cc -quiet -dumpdir
a- -dumpbase test.cc -dumpbase-ext .cc -mtune=generic -march=x86-64 -Os
-std=c++17 -fsyntax-only -o /dev/null
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
```
To reproduce:
```
/home/fuzz/WorkSpace/fusion-fuzz/projects/gcc/gcc-install/bin/g++ -fsyntax-only
./test.cc
```
Compiler version:
```
g++ (GCC) 17.0.0 20260917 (experimental)
Copyright (C) 2026 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```
Commit:
```
d373724d1ddeef9b322b6b6078fc1de8dbe27791
```
Build configuration:
```
./configure --enable-languages=c,c++ --disable-bootstrap
--enable-checking=yes,extra,rtl --disable-multilib --disable-libsanitizer
--disable-nls --disable-werror
```
Operating System:
```
Ubuntu 22.04 Host, Docker fusion-fuzz-gcc:latest
```
*This bug was found by
[fusion-fuzz](https://github.com/fusion-fuzz/fusion-fuzz)*
