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Date: Sun, 10 Feb 2013 23:31:41 +0100
From: Jens Gustedt <>
Subject: [PATCH 1/3] protect some clobbered variables with volatile

When switching optimization to higher levels (-O3) and enable link time
optimization (-flto) gcc finds two variables that might be clobbered
accross longjmp (orig_tail in dynlink) or vfork (f in popen):

src/ldso/dynlink.c:1014:27: warning: variable ‘orig_tail’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
src/stdio/popen.c:21:8: warning: variable ‘f’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]

Trust the analysis of the compiler and protect these variables with
volatile. Both variables are only loaded once or twice, so this should
never cause a performance penalty.

1	1	src/ldso/dynlink.c
1	1	src/stdio/popen.c

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index efbec8f..e19a21f 100644
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -1011,7 +1011,7 @@ void __init_ldso_ctors(void)
 void *dlopen(const char *file, int mode)
-	struct dso *volatile p, *orig_tail, *next;
+	struct dso *volatile p, *volatile orig_tail, *next;
 	size_t orig_tls_cnt, orig_tls_offset, orig_tls_align;
 	size_t i;
 	int cs;
diff --git a/src/stdio/popen.c b/src/stdio/popen.c
index ed20f5a..e5fbc4f 100644
--- a/src/stdio/popen.c
+++ b/src/stdio/popen.c
@@ -18,7 +18,7 @@ FILE *popen(const char *cmd, const char *mode)
 	int p[2], op, i;
 	pid_t pid;
-	FILE *f;
+	FILE *volatile f;
 	sigset_t old;
 	const char *modes = "rw", *mi = strchr(modes, *mode);

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