https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118927
Bug ID: 118927
Summary: "double free detected in tcache 2" with import std and
-Q
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: nate at thatsmathematics dot com
Target Milestone: ---
Created attachment 60523
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60523&action=edit
Main source file foo.cc
I was trying to use gcc 15 trunk (commit 101e3101e) on arm64 gentoo (vm on
Apple M3) to compile the following code from a recent article by Stroustrup
(https://cacm.acm.org/blogcacm/21st-century-c/):
import std; // make all of the standard library available
using namespace std;
int main() // print unique lines from input
{ unordered_map<string,int> m; // hash table
for (string line; getline (cin,line); )
if (m[line]++ == 0)
cout<<line<<'\n';
}
Following the suggestion at
https://stackoverflow.com/questions/76154680/how-to-use-module-std-with-gcc, I
used
g++ -Q -std=c++20 -fmodules -fsearch-include-path bits/std.cc foo.cc
The compile fails with "free(): double free detected in tcache 2" and the
following backtrace:
0x259e35b internal_error(char const*, ...)
../../gcc/diagnostic-global-context.cc:517
0x12a617b crash_signal
../../gcc/toplev.cc:322
0xb54343 cxx_printable_name_internal
../../gcc/cp/tree.cc:2768
0x12a6a3f announce_function(tree_node*)
../../gcc/toplev.cc:230
0x8ddd03 start_preparsed_function(tree_node*, tree_node*, int)
../../gcc/cp/decl.cc:18590
0x9feb17 maybe_clone_body(tree_node*)
../../gcc/cp/optimize.cc:585
0x9a8f87 post_load_processing
../../gcc/cp/module.cc:18834
0x9d81ef lazy_load_pendings(tree_node*)
../../gcc/cp/module.cc:20769
0xabd3a7 lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int)
../../gcc/cp/pt.cc:10241
0xac04cf tsubst(tree_node*, tree_node*, int, tree_node*)
../../gcc/cp/pt.cc:16549
0xac08bf tsubst_entering_scope
../../gcc/cp/pt.cc:10095
0xac08bf tsubst(tree_node*, tree_node*, int, tree_node*)
../../gcc/cp/pt.cc:17092
0x93ea8f dump_template_bindings
../../gcc/cp/error.cc:596
0x933b6f dump_function_decl
../../gcc/cp/error.cc:1982
0x93fb27 decl_as_string(tree_node*, int)
../../gcc/cp/error.cc:3334
0x93fb27 lang_decl_name(tree_node*, int, bool)
../../gcc/cp/error.cc:3369
0xb5435b cxx_printable_name_internal
../../gcc/cp/tree.cc:2770
0x12a6a3f announce_function(tree_node*)
../../gcc/toplev.cc:230
0x8ddd03 start_preparsed_function(tree_node*, tree_node*, int)
../../gcc/cp/decl.cc:18590
0x9feb17 maybe_clone_body(tree_node*)
../../gcc/cp/optimize.cc:585
When -Q is omitted, the program compiles and runs correctly.
g++ -v output:
Using built-in specs.
COLLECT_GCC=/home/nate/do-not-backup/gcc-inst/bin/g++
COLLECT_LTO_WRAPPER=/home/nate/do-not-backup/gcc-inst/libexec/gcc/aarch64-unknown-linux-gnu/15.0.1/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../configure --enable-checking --enable-languages=c++
--prefix=/home/nate/do-not-backup/gcc-inst
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.1 20250218 (experimental) (GCC)
