From 2bb5abedbdeed964adb81d2a0284db872e25a329 Mon Sep 17 00:00:00 2001
From: Dan Gohman <dev@sunfishcode.online>
Date: Mon, 28 Nov 2022 13:50:04 -0800
Subject: [PATCH] Define an `__errno_location` function. (#347)

This function returns the address of `errno`, which makes it easier to
access from non-C languages since `errno` is a thread-local variable
which requires a special ABI.
---
 expected/wasm32-wasi/posix/defined-symbols.txt  | 1 +
 expected/wasm32-wasi/single/defined-symbols.txt | 1 +
 libc-bottom-half/sources/__errno_location.c     | 5 +++++
 3 files changed, 7 insertions(+)
 create mode 100644 libc-bottom-half/sources/__errno_location.c

diff --git a/expected/wasm32-wasi/posix/defined-symbols.txt b/expected/wasm32-wasi/posix/defined-symbols.txt
index d92bcbd88..645e44c64 100644
--- a/expected/wasm32-wasi/posix/defined-symbols.txt
+++ b/expected/wasm32-wasi/posix/defined-symbols.txt
@@ -48,6 +48,7 @@ __do_des
 __do_orphaned_stdio_locks
 __duplocale
 __env_rm_add
+__errno_location
 __exp2f_data
 __exp_data
 __expo2
diff --git a/expected/wasm32-wasi/single/defined-symbols.txt b/expected/wasm32-wasi/single/defined-symbols.txt
index f8f445707..2e890a049 100644
--- a/expected/wasm32-wasi/single/defined-symbols.txt
+++ b/expected/wasm32-wasi/single/defined-symbols.txt
@@ -38,6 +38,7 @@ __des_setkey
 __do_des
 __duplocale
 __env_rm_add
+__errno_location
 __exp2f_data
 __exp_data
 __expo2
diff --git a/libc-bottom-half/sources/__errno_location.c b/libc-bottom-half/sources/__errno_location.c
new file mode 100644
index 000000000..5e6ef5e6b
--- /dev/null
+++ b/libc-bottom-half/sources/__errno_location.c
@@ -0,0 +1,5 @@
+#include <errno.h>
+
+int *__errno_location(void) {
+    return &errno;
+}