From 613a6c473fb61893f29132638cc8051ab0f4d019 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 25 Mar 2026 16:42:21 +0300
Subject: [PATCH] pref: fix undefined reference to tcc_backtrace when linking
 (fixes #23198)

---
 vlib/v/pref/default.v                         |  9 +++
 vlib/v/pref/pref_test.v                       | 17 ++++++
 .../v/tests/shared_library_system_link_test.v | 56 +++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 vlib/v/tests/shared_library_system_link_test.v

diff --git a/vlib/v/pref/default.v b/vlib/v/pref/default.v
index c01748c1c..a1b378089 100644
--- a/vlib/v/pref/default.v
+++ b/vlib/v/pref/default.v
@@ -96,6 +96,14 @@ pub fn (mut p Preferences) defines_map_unique_keys() string {
 	return skeys.join(',')
 }
 
+fn (mut p Preferences) disable_tcc_shared_backtraces() {
+	if p.is_shared && p.ccompiler_type == .tinyc && 'no_backtrace' !in p.compile_defines_all {
+		// TCC shared libraries should not depend on TCC's backtrace runtime symbols.
+		p.parse_define('no_backtrace')
+	}
+}
+
+// fill_with_defaults initializes unset preferences and derives build options from them.
 pub fn (mut p Preferences) fill_with_defaults() {
 	p.setup_os_and_arch_when_not_explicitly_set()
 	p.expand_lookup_paths()
@@ -171,6 +179,7 @@ pub fn (mut p Preferences) fill_with_defaults() {
 	}
 	p.find_cc_if_cross_compiling()
 	p.ccompiler_type = cc_from_string(p.ccompiler)
+	p.disable_tcc_shared_backtraces()
 	p.is_test = p.path.ends_with('_test.v') || p.path.ends_with('_test.vv')
 		|| p.path.all_before_last('.v').all_before_last('.').ends_with('_test')
 	p.is_vsh = p.path.ends_with('.vsh') || p.raw_vsh_tmp_prefix != ''
diff --git a/vlib/v/pref/pref_test.v b/vlib/v/pref/pref_test.v
index 7fc86ae7d..6515374d4 100644
--- a/vlib/v/pref/pref_test.v
+++ b/vlib/v/pref/pref_test.v
@@ -194,3 +194,20 @@ fn test_output_flag_accepts_directory_path() {
 	}
 	assert os.is_file(expected_output)
 }
+
+fn test_tcc_shared_builds_disable_backtraces() {
+	mut shared_prefs := &pref.Preferences{
+		path:      'libfoo.v'
+		is_shared: true
+		ccompiler: 'tinyc'
+	}
+	shared_prefs.fill_with_defaults()
+	assert 'no_backtrace' in shared_prefs.compile_defines_all
+
+	mut regular_prefs := &pref.Preferences{
+		path:      'main.v'
+		ccompiler: 'tinyc'
+	}
+	regular_prefs.fill_with_defaults()
+	assert 'no_backtrace' !in regular_prefs.compile_defines_all
+}
diff --git a/vlib/v/tests/shared_library_system_link_test.v b/vlib/v/tests/shared_library_system_link_test.v
new file mode 100644
index 000000000..fb555e158
--- /dev/null
+++ b/vlib/v/tests/shared_library_system_link_test.v
@@ -0,0 +1,56 @@
+import os
+import rand
+
+const vexe = @VEXE
+
+fn test_shared_library_links_with_system_cc() {
+	if os.user_os() != 'linux' {
+		return
+	}
+	workdir := os.join_path(os.vtmp_dir(), 'v_shared_link_${rand.ulid()}')
+	os.mkdir_all(workdir) or { panic(err) }
+	defer {
+		os.rmdir_all(workdir) or {}
+	}
+	lib_src := os.join_path(workdir, 'libfoo.v')
+	lib_out := os.join_path(workdir, 'libfoo')
+	lib_so := '${lib_out}.so'
+	host_src := os.join_path(workdir, 'host.c')
+	host_bin := os.join_path(workdir, 'host')
+	os.write_file(lib_src, [
+		'module libfoo',
+		'',
+		'pub fn square(x int) int {',
+		'\treturn x * x',
+		'}',
+	].join('\n')) or { panic(err) }
+	os.write_file(host_src, [
+		'#include <stdio.h>',
+		'',
+		'int libfoo__square(int);',
+		'',
+		'int main(void) {',
+		'\tprintf("%d\\n", libfoo__square(2));',
+		'\treturn 0;',
+		'}',
+	].join('\n')) or { panic(err) }
+	run_cmd('${os.quoted_path(vexe)} -shared -o ${os.quoted_path(lib_out)} ${os.quoted_path(lib_src)}') or {
+		panic(err)
+	}
+	assert os.exists(lib_so)
+	run_cmd('cc ${os.quoted_path(host_src)} -L${os.quoted_path(workdir)} -lfoo -o ${os.quoted_path(host_bin)}') or {
+		panic(err)
+	}
+	res := run_cmd('LD_LIBRARY_PATH=${os.quoted_path(workdir)} ${os.quoted_path(host_bin)}') or {
+		panic(err)
+	}
+	assert res.output.trim_space() == '4'
+}
+
+fn run_cmd(cmd string) !os.Result {
+	res := os.execute(cmd)
+	if res.exit_code != 0 {
+		return error('command failed:\n${cmd}\n${res.output}')
+	}
+	return res
+}
-- 
2.39.5