[PATCH] features: version-gate _DYNAMIC_STACK_SIZE_SOURCE

[Andrew Kelley <andrew@ziglang.org>]

Without this patch, software compiled against glibc 2.34 headers but
then executed on a system with an older glibc version will attempt to
invoke `sysconf(_SC_SIGSTKSZ)` when MINSIGSTKSZ or SIGSTKSZ are used. On
glibcs older than 2.34, this will return -1 (with an errno of EINVAL),
effectively causing MINSIGSTKSZ and SIGSTKSZ to have the value of -1.

This patch version-gates the _DYNAMIC_STACK_SIZE_SOURCE preprocessor
definition so that this problem cannot occur.

Downstream patch:
https://github.com/ziglang/zig/commit/39083c31a550ed80f369f60d35791e98904b8096
---
 include/features.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/features.h b/include/features.h
index ab2b2caac4..77a8f8cc32 100644
--- a/include/features.h
+++ b/include/features.h
@@ -220,8 +220,10 @@
 # define _DEFAULT_SOURCE	1
 # undef  _ATFILE_SOURCE
 # define _ATFILE_SOURCE	1
-# undef  _DYNAMIC_STACK_SIZE_SOURCE
-# define _DYNAMIC_STACK_SIZE_SOURCE 1
+# if __GNUC_PREREQ (2,34)
+#  undef  _DYNAMIC_STACK_SIZE_SOURCE
+#  define _DYNAMIC_STACK_SIZE_SOURCE 1
+# endif
 #endif
 
 /* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined,
-- 
2.33.1