From 6cdb407aa23d8b129e9b9a49a4528c3e0def69e6 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Fri, 19 Apr 2024 14:15:30 -0400
Subject: config: Check for strerror_[lr]()

---
 config/header.mk          |  6 +++++-
 config/strerror-l.c       | 11 +++++++++++
 config/strerror-r-gnu.c   | 11 +++++++++++
 config/strerror-r-posix.c | 11 +++++++++++
 config/uselocale.c        |  9 +++++++++
 src/bfstd.c               | 42 ++++++++++++++++++++----------------------
 6 files changed, 67 insertions(+), 23 deletions(-)
 create mode 100644 config/strerror-l.c
 create mode 100644 config/strerror-r-gnu.c
 create mode 100644 config/strerror-r-posix.c
 create mode 100644 config/uselocale.c

diff --git a/config/header.mk b/config/header.mk
index 55657f8..36ad98e 100644
--- a/config/header.mk
+++ b/config/header.mk
@@ -20,7 +20,11 @@ HEADERS := \
     ${GEN}/posix-spawn-addfchdir.h \
     ${GEN}/posix-spawn-addfchdir-np.h \
     ${GEN}/statx.h \
-    ${GEN}/statx-syscall.h
+    ${GEN}/statx-syscall.h \
+    ${GEN}/strerror-l.h \
+    ${GEN}/strerror-r-gnu.h \
+    ${GEN}/strerror-r-posix.h \
+    ${GEN}/uselocale.h
 
 ${GEN}/config.h: ${HEADERS}
 	${MSG} "[ GEN] ${TGT}"
diff --git a/config/strerror-l.c b/config/strerror-l.c
new file mode 100644
index 0000000..3dcc4d7
--- /dev/null
+++ b/config/strerror-l.c
@@ -0,0 +1,11 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <errno.h>
+#include <locale.h>
+#include <string.h>
+
+int main(void) {
+	locale_t locale = duplocale(LC_GLOBAL_LOCALE);
+	return !strerror_l(ENOMEM, locale);
+}
diff --git a/config/strerror-r-gnu.c b/config/strerror-r-gnu.c
new file mode 100644
index 0000000..26ca0ee
--- /dev/null
+++ b/config/strerror-r-gnu.c
@@ -0,0 +1,11 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <errno.h>
+#include <string.h>
+
+int main(void) {
+	char buf[256];
+	// Check that strerror_r() returns a pointer
+	return *strerror_r(ENOMEM, buf, sizeof(buf));
+}
diff --git a/config/strerror-r-posix.c b/config/strerror-r-posix.c
new file mode 100644
index 0000000..41b2d30
--- /dev/null
+++ b/config/strerror-r-posix.c
@@ -0,0 +1,11 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <errno.h>
+#include <string.h>
+
+int main(void) {
+	char buf[256];
+	// Check that strerror_r() returns an integer
+	return 2 * strerror_r(ENOMEM, buf, sizeof(buf));
+}
diff --git a/config/uselocale.c b/config/uselocale.c
new file mode 100644
index 0000000..a712ff8
--- /dev/null
+++ b/config/uselocale.c
@@ -0,0 +1,9 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <locale.h>
+
+int main(void) {
+	locale_t locale = uselocale((locale_t)0);
+	return locale == LC_GLOBAL_LOCALE;
+}
diff --git a/src/bfstd.c b/src/bfstd.c
index e2c2b97..1144380 100644
--- a/src/bfstd.c
+++ b/src/bfstd.c
@@ -317,35 +317,33 @@ const char *xstrerror(int errnum) {
 	const char *ret = NULL;
 	static thread_local char buf[256];
 
-	// - __APPLE__
-	// - __COSMOPOLITAN__
-	//     - No strerror_l()
-	// - __FreeBSD__ && SANITIZE_MEMORY
-	//     - duplocale() triggers https://github.com/llvm/llvm-project/issues/65532
-#if __APPLE__ || __COSMOPOLITAN__ || (__FreeBSD__ && SANITIZE_MEMORY)
-	if (strerror_r(errnum, buf, sizeof(buf)) == 0) {
-		ret = buf;
-	}
-#else
-#  if __NetBSD__
-	// NetBSD has no thread-specific locales
-	locale_t loc = LC_GLOBAL_LOCALE;
-#  else
+	// On FreeBSD with MemorySanitizer, duplocale() triggers
+	// https://github.com/llvm/llvm-project/issues/65532
+#if BFS_HAS_STRERROR_L && !(__FreeBSD__ && SANITIZE_MEMORY)
+#  if BFS_HAS_USELOCALE
 	locale_t loc = uselocale((locale_t)0);
+#  else
+	locale_t loc = LC_GLOBAL_LOCALE;
 #  endif
 
-	locale_t copy = loc;
-	if (copy == LC_GLOBAL_LOCALE) {
-		copy = duplocale(copy);
+	bool free_loc = false;
+	if (loc == LC_GLOBAL_LOCALE) {
+		loc = duplocale(loc);
+		free_loc = true;
 	}
 
-	if (copy != (locale_t)0) {
-		ret = strerror_l(errnum, copy);
-
-		if (loc == LC_GLOBAL_LOCALE) {
-			freelocale(copy);
+	if (loc != (locale_t)0) {
+		ret = strerror_l(errnum, loc);
+		if (free_loc) {
+			freelocale(loc);
 		}
 	}
+#elif BFS_HAS_STRERROR_R_POSIX
+	if (strerror_r(errnum, buf, sizeof(buf)) == 0) {
+		ret = buf;
+	}
+#elif BFS_HAS_STRERROR_R_GNU
+	ret = strerror_r(errnum, buf, sizeof(buf));
 #endif
 
 	if (!ret) {
-- 
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