net.mbedtls: enable MBEDTLS_THREADING_C on Windows and macOS

thirdparty/mbedtls/include/mbedtls/mbedtls_config.h

@@ -4457,9 +4457,15 @@
 #define MBEDTLS_PADLOCK_C
 #endif // __TINYC__
 
-#if ( defined(__linux__) || defined(__FreeBSD__) ) || defined (__OpenBSD__)
+#if ( defined(__linux__) || defined(__FreeBSD__) ) || defined (__OpenBSD__) || defined(__APPLE__)
 #define MBEDTLS_THREADING_PTHREAD
 #define MBEDTLS_THREADING_C
+#elif defined(_WIN32)
+// Windows has no pthreads; the mutex callbacks are provided via
+// MBEDTLS_THREADING_ALT (see vlib/net/mbedtls/mbedtls_threading.h, installed by
+// mbedtls_threading_set_alt() from the net.mbedtls module init()).
+#define MBEDTLS_THREADING_ALT
+#define MBEDTLS_THREADING_C
 #else
 #undef MBEDTLS_THREADING_PTHREAD
 #undef MBEDTLS_THREADING_C

thirdparty/mbedtls/include/mbedtls/threading_alt.h

@@ -0,0 +1,20 @@
+/*
+ * threading_alt.h - mbedtls_threading_mutex_t for MBEDTLS_THREADING_ALT.
+ *
+ * V provides this on Windows (which has no pthreads) so that
+ * MBEDTLS_THREADING_C can be enabled. The mutex is a Win32 CRITICAL_SECTION;
+ * the callbacks that operate on it live in
+ * vlib/net/mbedtls/mbedtls_threading.h and are installed once at startup via
+ * mbedtls_threading_set_alt() from the net.mbedtls module init().
+ */
+#ifndef MBEDTLS_THREADING_ALT_H
+#define MBEDTLS_THREADING_ALT_H
+
+#include <windows.h>
+
+typedef struct mbedtls_threading_mutex_t {
+    CRITICAL_SECTION cs;
+    char is_valid;
+} mbedtls_threading_mutex_t;
+
+#endif /* MBEDTLS_THREADING_ALT_H */

thirdparty/mbedtls/mbedtls.patch

@@ -18,7 +18,7 @@ diff -ur mbedtls.orig/include/mbedtls/check_config.h mbedtls/include/mbedtls/che
 diff -ur mbedtls.orig/include/mbedtls/mbedtls_config.h mbedtls/include/mbedtls/mbedtls_config.h
 --- mbedtls.orig/include/mbedtls/mbedtls_config.h	2026-04-02 17:26:31.910276365 +0200
 +++ mbedtls/include/mbedtls/mbedtls_config.h	2026-04-02 17:27:29.374384448 +0200
-@@ -4435,3 +4435,22 @@
+@@ -4435,3 +4435,28 @@
  //#define MBEDTLS_X509_MAX_FILE_PATH_LEN     512 /**< Maximum length of a path/filename string in bytes including the null terminator character ('\0'). */
 
  /** \} name SECTION: Module configuration options */
@@ -34,13 +34,43 @@ diff -ur mbedtls.orig/include/mbedtls/mbedtls_config.h mbedtls/include/mbedtls/m
 +#define MBEDTLS_PADLOCK_C
 +#endif // __TINYC__
 +
-+#if ( defined(__linux__) || defined(__FreeBSD__) ) || defined (__OpenBSD__)
++#if ( defined(__linux__) || defined(__FreeBSD__) ) || defined (__OpenBSD__) || defined(__APPLE__)
 +#define MBEDTLS_THREADING_PTHREAD
 +#define MBEDTLS_THREADING_C
++#elif defined(_WIN32)
++// Windows has no pthreads; the mutex callbacks are provided via
++// MBEDTLS_THREADING_ALT (see vlib/net/mbedtls/mbedtls_threading.h, installed by
++// mbedtls_threading_set_alt() from the net.mbedtls module init()).
++#define MBEDTLS_THREADING_ALT
++#define MBEDTLS_THREADING_C
 +#else
 +#undef MBEDTLS_THREADING_PTHREAD
 +#undef MBEDTLS_THREADING_C
 +#endif
+diff -ur mbedtls.orig/include/mbedtls/threading_alt.h mbedtls/include/mbedtls/threading_alt.h
+--- mbedtls.orig/include/mbedtls/threading_alt.h	1970-01-01 00:00:00.000000000 +0000
++++ mbedtls/include/mbedtls/threading_alt.h	2026-06-12 00:00:00.000000000 +0000
+@@ -0,0 +1,20 @@
++/*
++ * threading_alt.h - mbedtls_threading_mutex_t for MBEDTLS_THREADING_ALT.
++ *
++ * V provides this on Windows (which has no pthreads) so that
++ * MBEDTLS_THREADING_C can be enabled. The mutex is a Win32 CRITICAL_SECTION;
++ * the callbacks that operate on it live in
++ * vlib/net/mbedtls/mbedtls_threading.h and are installed once at startup via
++ * mbedtls_threading_set_alt() from the net.mbedtls module init().
++ */
++#ifndef MBEDTLS_THREADING_ALT_H
++#define MBEDTLS_THREADING_ALT_H
++
++#include <windows.h>
++
++typedef struct mbedtls_threading_mutex_t {
++    CRITICAL_SECTION cs;
++    char is_valid;
++} mbedtls_threading_mutex_t;
++
++#endif /* MBEDTLS_THREADING_ALT_H */
 diff -ur mbedtls.orig/library/alignment.h mbedtls/library/alignment.h
 --- mbedtls.orig/library/alignment.h	2026-04-02 17:26:31.918276380 +0200
 +++ mbedtls/library/alignment.h	2026-04-02 17:30:51.350689732 +0200

vlib/net/mbedtls/mbedtls.c.v

@@ -135,7 +135,21 @@ $if prod && opt_size ? {
 #include <mbedtls/entropy.h>
 #include <mbedtls/ctr_drbg.h>
 #include <mbedtls/error.h>
+#include <mbedtls/threading.h>
 #insert "@VEXEROOT/vlib/net/mbedtls/mbedtls_helpers.h"
+#insert "@VEXEROOT/vlib/net/mbedtls/mbedtls_threading.h"
+
+// v_mbedtls_threading_setup installs the mutex callbacks mbedtls needs when it
+// is built with MBEDTLS_THREADING_ALT (Windows). On platforms that use pthread
+// threading or no threading it is a no-op. Defined in mbedtls_threading.h.
+fn C.v_mbedtls_threading_setup()
+
+// init installs mbedtls' thread-safety callbacks once, before any TLS use, so
+// the library's shared state (RNG, key blinding, internal globals) is safe to
+// use across threads. A no-op on non-Windows builds.
+fn init() {
+	C.v_mbedtls_threading_setup()
+}
 
 @[typedef]
 pub struct C.mbedtls_net_context {

vlib/net/mbedtls/mbedtls_threading.h

@@ -0,0 +1,62 @@
+/*
+ * mbedtls_threading.h - Win32 mutex callbacks for MBEDTLS_THREADING_ALT.
+ *
+ * On Windows, mbedtls is built with MBEDTLS_THREADING_C + MBEDTLS_THREADING_ALT
+ * (see thirdparty/mbedtls/include/mbedtls/mbedtls_config.h). The library then
+ * expects the embedder to supply the four mutex primitives via
+ * mbedtls_threading_set_alt(). These wrap a Win32 CRITICAL_SECTION; the matching
+ * mbedtls_threading_mutex_t type is defined in
+ * thirdparty/mbedtls/include/mbedtls/threading_alt.h.
+ *
+ * v_mbedtls_threading_setup() is called once from net.mbedtls' init() before any
+ * TLS use. On every other platform it is a no-op (pthread threading, or none).
+ */
+#ifndef V_MBEDTLS_THREADING_H
+#define V_MBEDTLS_THREADING_H
+
+#if defined(_WIN32) && defined(MBEDTLS_THREADING_ALT)
+
+#include <windows.h>
+#include <mbedtls/threading.h>
+#include <mbedtls/error.h>
+
+static void v_mbedtls_mutex_init(mbedtls_threading_mutex_t *m) {
+    InitializeCriticalSection(&m->cs);
+    m->is_valid = 1;
+}
+
+static void v_mbedtls_mutex_free(mbedtls_threading_mutex_t *m) {
+    if (m->is_valid) {
+        DeleteCriticalSection(&m->cs);
+        m->is_valid = 0;
+    }
+}
+
+static int v_mbedtls_mutex_lock(mbedtls_threading_mutex_t *m) {
+    if (!m->is_valid) {
+        return MBEDTLS_ERR_THREADING_BAD_INPUT_DATA;
+    }
+    EnterCriticalSection(&m->cs);
+    return 0;
+}
+
+static int v_mbedtls_mutex_unlock(mbedtls_threading_mutex_t *m) {
+    if (!m->is_valid) {
+        return MBEDTLS_ERR_THREADING_BAD_INPUT_DATA;
+    }
+    LeaveCriticalSection(&m->cs);
+    return 0;
+}
+
+static void v_mbedtls_threading_setup(void) {
+    mbedtls_threading_set_alt(v_mbedtls_mutex_init, v_mbedtls_mutex_free,
+        v_mbedtls_mutex_lock, v_mbedtls_mutex_unlock);
+}
+
+#else /* not (Windows + THREADING_ALT) */
+
+static void v_mbedtls_threading_setup(void) { }
+
+#endif
+
+#endif /* V_MBEDTLS_THREADING_H */

vlib/v/builder/builder.v

@@ -59,6 +59,10 @@ pub mut:
 	str_args              string              // for parallel_cc mode only, to know which cc args to use (like -I etc)
 	last_cc_cmd           string              // the most recently executed C compiler command; reused to regenerate a #line annotated report
 	disable_flto          bool
+	// thirdparty_header_mtimes memoizes the newest header mtime under a
+	// thirdparty module root (see thirdparty_deps_mtime), so the recursive scan
+	// runs once per module instead of once per compiled object.
+	thirdparty_header_mtimes map[string]i64
 }
 
 struct CFunctionCallCollector {

vlib/v/builder/cc.v

@@ -2400,28 +2400,50 @@ fn (v &Builder) should_compile_bundled_thirdparty_object_from_source(obj_path st
 	return v.ccoptions.cc == .tcc && v.pref.os == .macos
 }
 
-// latest_thirdparty_header_mtime returns the most recent mtime among `.h` and
-// `.hpp` files in the directory of `source_file`. It is used as an extra cache
-// key for third-party object compilation, so that header-only patches (for
-// example to mbedtls/library/alignment.h) reliably invalidate stale `.o`
-// files that were produced before the header change.
-fn latest_thirdparty_header_mtime(source_file string) i64 {
+// thirdparty_module_root returns the `thirdparty/<module>` directory that
+// `source_file` belongs to, or its own directory when the path is not under a
+// `thirdparty/` tree (so the scan degrades to the old source-dir-only behavior).
+fn thirdparty_module_root(source_file string) string {
+	norm := source_file.replace('\\', '/')
+	marker := '/thirdparty/'
+	idx := norm.index(marker) or { return os.dir(source_file) }
+	rest := norm[idx + marker.len..]
+	mod_name := rest.all_before('/')
+	if mod_name == '' || mod_name == rest {
+		// No further path component after the module name: fall back.
+		return os.dir(source_file)
+	}
+	return norm[..idx] + marker + mod_name
+}
+
+// thirdparty_deps_mtime returns the newest mtime among `source_file` itself and
+// every `.h`/`.hpp` header under its thirdparty module root. It is the shared
+// cache key for third-party object compilation (both the C and MSVC paths), so
+// that header-only edits anywhere in the module — including config headers under
+// `include/`, e.g. mbedtls/include/mbedtls/mbedtls_config.h, not just siblings
+// of the `.c` — reliably invalidate stale objects built before the change. The
+// recursive header scan is memoized per module root.
+fn (mut v Builder) thirdparty_deps_mtime(source_file string) i64 {
 	if source_file == '' {
 		return 0
 	}
-	dir := os.dir(source_file)
-	entries := os.ls(dir) or { return 0 }
-	mut latest := i64(0)
-	for f in entries {
-		if !(f.ends_with('.h') || f.ends_with('.hpp')) {
-			continue
-		}
-		m := os.file_last_mod_unix(os.join_path(dir, f))
-		if m > latest {
-			latest = m
+	src_mtime := os.file_last_mod_unix(source_file)
+	root := thirdparty_module_root(source_file)
+	hdr_mtime := v.thirdparty_header_mtimes[root] or {
+		mut latest := i64(0)
+		for f in os.walk_ext(root, '') {
+			if !(f.ends_with('.h') || f.ends_with('.hpp')) {
+				continue
+			}
+			m := os.file_last_mod_unix(f)
+			if m > latest {
+				latest = m
+			}
 		}
+		v.thirdparty_header_mtimes[root] = latest
+		latest
 	}
-	return latest
+	return if hdr_mtime > src_mtime { hdr_mtime } else { src_mtime }
 }
 
 fn (mut v Builder) build_thirdparty_obj_file(mod string, path string, moduleflags []cflag.CFlag) {
@@ -2472,14 +2494,12 @@ fn (mut v Builder) build_thirdparty_obj_file(mod string, path string, moduleflag
 	}
 	if os.exists(opath) {
 		opath_mtime := os.file_last_mod_unix(opath)
-		src_mtime := os.file_last_mod_unix(source_file)
-		// Header-only edits in the source directory (e.g. mbedtls's
-		// alignment.h) leave every sibling `.c` untouched, so a pure
+		// Header-only edits (e.g. mbedtls's alignment.h, or a config header
+		// under include/) leave every `.c` untouched, so a pure
 		// `opath_mtime < src_mtime` test would silently reuse stale objects
-		// that still reference the old headers. Treat the newest sibling
-		// header as part of the cache key as well.
-		hdr_mtime := latest_thirdparty_header_mtime(source_file)
-		deps_mtime := if hdr_mtime > src_mtime { hdr_mtime } else { src_mtime }
+		// that still reference the old headers. Fold the newest module header
+		// into the cache key as well.
+		deps_mtime := v.thirdparty_deps_mtime(source_file)
 		if compile_bundled_source && !cached_object_was_built_from_source {
 			rebuild_reason_message = '${os.quoted_path(opath)} was copied from a bundled object, rebuilding it from ${os.quoted_path(source_file)} ...'
 		} else if opath_mtime < deps_mtime {

vlib/v/builder/cc_test.v

@@ -1,6 +1,7 @@
 module builder
 
 import os
+import time
 import v.pref
 
 fn test_ccompiler_is_available_with_existing_absolute_path() {
@@ -775,6 +776,54 @@ fn test_c_error_should_send_bug_report_for_regular_c_error() {
 	assert c_error_should_send_bug_report(c_output)
 }
 
+fn test_thirdparty_module_root_spans_library_and_include() {
+	// A source under library/ resolves to the whole `thirdparty/<mod>` root, so a
+	// sibling include/ tree (e.g. mbedtls config headers) is in scope when
+	// computing the object's header-dependency mtime.
+	assert thirdparty_module_root('/x/y/thirdparty/mbedtls/library/aes.c') == '/x/y/thirdparty/mbedtls'
+	// Windows-style separators are normalized to forward slashes.
+	assert thirdparty_module_root('S:\\repo\\thirdparty\\mbedtls\\include\\mbedtls\\cfg.h') == 'S:/repo/thirdparty/mbedtls'
+	// A path that is not under a thirdparty/ tree falls back to the source dir.
+	assert thirdparty_module_root('/tmp/foo/bar.c') == os.dir('/tmp/foo/bar.c')
+}
+
+// Regression guard for vlang/v#27437: thirdparty objects must rebuild when a
+// header anywhere in the module changes, including config headers under
+// include/ (not just siblings of the .c). thirdparty_deps_mtime is the shared
+// cache key for both the C and MSVC object paths, so this protects both.
+fn test_thirdparty_deps_mtime_includes_module_include_headers() {
+	test_root := os.join_path(os.vtmp_dir(), 'v_builder_thirdparty_deps_${os.getpid()}')
+	os.rmdir_all(test_root) or {}
+	defer {
+		os.rmdir_all(test_root) or {}
+	}
+	lib_dir := os.join_path(test_root, 'thirdparty', 'mymod', 'library')
+	inc_dir := os.join_path(test_root, 'thirdparty', 'mymod', 'include', 'mymod')
+	os.mkdir_all(lib_dir) or { panic(err) }
+	os.mkdir_all(inc_dir) or { panic(err) }
+	source := os.join_path(lib_dir, 'foo.c')
+	sibling := os.join_path(lib_dir, 'foo.h')
+	os.write_file(source, 'int foo(void){return 0;}') or { panic(err) }
+	os.write_file(sibling, '/* sibling header */') or { panic(err) }
+	// file_last_mod_unix is second-resolution, so a >1s gap is needed for the
+	// config header to be observably newer than the source.
+	time.sleep(1100 * time.millisecond)
+	config := os.join_path(inc_dir, 'mymod_config.h')
+	os.write_file(config, '#define MYMOD 1') or { panic(err) }
+
+	mut b := new_builder_for_args([hello_world_example()])
+	deps := b.thirdparty_deps_mtime(source)
+	config_mtime := os.file_last_mod_unix(config)
+	source_mtime := os.file_last_mod_unix(source)
+	assert config_mtime > source_mtime, 'precondition: the include/ config header must be newer than the source'
+	// The config header lives under include/, not in the source directory, yet
+	// the dependency mtime must still reflect it — otherwise stale objects are
+	// reused after a config-header change (the bug this fix addresses).
+	assert deps == config_mtime, 'thirdparty_deps_mtime must fold in include/ headers; got ${deps}, want ${config_mtime}'
+	// Memoized per module root: a second call returns the same value.
+	assert b.thirdparty_deps_mtime(source) == config_mtime
+}
+
 fn prepare_test_ccompiler_alias(test_root string, compiler_name string, version_output string) string {
 	os.rmdir_all(test_root) or {}
 	os.mkdir_all(test_root) or { panic(err) }

vlib/v/builder/msvc_windows.v

@@ -442,18 +442,28 @@ fn (mut v Builder) build_thirdparty_obj_file_with_msvc(mod string, path string,
 	trace_thirdparty_obj_files := 'trace_thirdparty_obj_files' in v.pref.compile_defines
 	path_without_o_postfix := path.all_before_last('.')
 	obj_path := v.msvc_thirdparty_obj_path(mod, path, '')
-	if os.exists(obj_path) {
-		// println('${obj_path} already built.')
-		return
-	}
-	if trace_thirdparty_obj_files {
-		println('${obj_path} not found, building it (with msvc)...')
-	}
 	cfile := if os.exists('${path_without_o_postfix}.c') {
 		'${path_without_o_postfix}.c'
 	} else {
 		'${path_without_o_postfix}.cpp'
 	}
+	if os.exists(obj_path) {
+		// Reuse the cached object only when it is newer than its source and
+		// every header in the thirdparty module (config headers under include/
+		// included; see thirdparty_deps_mtime). Without this, a config/header
+		// change silently keeps a stale `.obj` — the long-standing `-cc msvc`
+		// "delete library/*.obj by hand" footgun. Source-less bundled objects
+		// (no sibling .c/.cpp) keep the previous reuse-if-present behavior.
+		src_exists := os.exists('${path_without_o_postfix}.c')
+			|| os.exists('${path_without_o_postfix}.cpp')
+		if !src_exists || os.file_last_mod_unix(obj_path) >= v.thirdparty_deps_mtime(cfile) {
+			// println('${obj_path} already built.')
+			return
+		}
+	}
+	if trace_thirdparty_obj_files {
+		println('${obj_path} not found or stale, building it (with msvc)...')
+	}
 	flags := v.msvc_string_flags(moduleflags)
 	inc_dirs := flags.inc_paths.join(' ')
 	defines := flags.defines.join(' ')