From ea99f21ce6c8a332845439ea87f792dbaf679d42 Mon Sep 17 00:00:00 2001
From: Matt Joyce <matthew.joyce@embedded-brains.de>
Date: Mon, 16 May 2022 11:51:54 +0200
Subject: Add --enable-newlib-reent-thread-local option

By default, Newlib uses a huge object of type struct _reent to store
thread-specific data.  This object is returned by __getreent() if the
__DYNAMIC_REENT__ Newlib configuration option is defined.

The reentrancy structure contains for example errno and the standard input,
output, and error file streams.  This means that if an application only uses
errno it has a dependency on the file stream support even if it does not use
it.  This is an issue for lower end targets and applications which need to
qualify the software according to safety standards (for example ECSS-E-ST-40C,
ECSS-Q-ST-80C, IEC 61508, ISO 26262, DO-178, DO-330, DO-333).

If the new _REENT_THREAD_LOCAL configuration option is enabled, then struct
_reent is replaced by dedicated thread-local objects for each struct _reent
member.  The thread-local objects are defined in translation units which use
the corresponding object.
---
 newlib/configure | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'newlib/configure')

diff --git a/newlib/configure b/newlib/configure
index 82c256694..e493eb293 100755
--- a/newlib/configure
+++ b/newlib/configure
@@ -973,6 +973,7 @@ enable_newlib_atexit_dynamic_alloc
 enable_newlib_global_atexit
 enable_newlib_reent_small
 enable_newlib_reent_binary_compat
+enable_newlib_reent_thread_local
 enable_newlib_global_stdio_streams
 enable_newlib_fvwrite_in_streamio
 enable_newlib_fseek_optimization
@@ -1641,6 +1642,7 @@ Optional Features:
   --enable-newlib-global-atexit	enable atexit data structure as global
   --enable-newlib-reent-small   enable small reentrant struct support
   --enable-newlib-reent-binary-compat   enable backward binary compatibility for struct _reent
+  --enable-newlib-reent-thread-local   enable thread-local storage objects as a replacment for struct _reent members
   --enable-newlib-global-stdio-streams   enable global stdio streams
   --disable-newlib-fvwrite-in-streamio    disable iov in streamio
   --disable-newlib-fseek-optimization    disable fseek optimization
@@ -2404,6 +2406,19 @@ else
   newlib_reent_binary_compat=no
 fi
 
+# Check whether --enable-newlib-reent-thread-local was given.
+if test "${enable_newlib_reent_thread_local+set}" = set; then :
+  enableval=$enable_newlib_reent_thread_local; if test "${newlib_reent_thread_local+set}" != set; then
+  case "${enableval}" in
+    yes) newlib_reent_thread_local=yes ;;
+    no)  newlib_reent_thread_local=no  ;;
+    *)   as_fn_error $? "bad value ${enableval} for newlib-enable-reent-thread-local option" "$LINENO" 5 ;;
+  esac
+ fi
+else
+  newlib_reent_thread_local=no
+fi
+
 # Check whether --enable-newlib-global-stdio-streams was given.
 if test "${enable_newlib_global_stdio_streams+set}" = set; then :
   enableval=$enable_newlib_global_stdio_streams; case "${enableval}" in
@@ -6437,6 +6452,12 @@ $as_echo "#define _WANT_REENT_BACKWARD_BINARY_COMPAT 1" >>confdefs.h
 
 fi
 
+if test "${newlib_reent_thread_local}" = "yes"; then
+
+$as_echo "#define _WANT_REENT_THREAD_LOCAL 1" >>confdefs.h
+
+fi
+
 _mb_len_max=1
 if test "${newlib_mb}" = "yes"; then
 
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