Author: dim
Date: Thu Dec 15 19:42:25 2011
New Revision: 228536
URL: http://svn.freebsd.org/changeset/base/228536
Log:
The TCB_GET32() and TCB_GET64() macros in the i386 and amd64-specific
versions of pthread_md.h have a special case of dereferencing a null
pointer. Clang warns about this with:
In file included from lib/libthr/arch/i386/i386/pthread_md.c:36:
lib/libthr/arch/i386/include/pthread_md.h:96:10: error: indirection of
non-volatile null pointer will be deleted, not trap [-Werror,-Wnull-dereference]
return (TCB_GET32(tcb_self));
^~~~~~~~~~~~~~~~~~~
lib/libthr/arch/i386/include/pthread_md.h:73:13: note: expanded from:
: "m" (*(u_int *)(__tcb_offset(name)))); \
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lib/libthr/arch/i386/include/pthread_md.h:96:10: note: consider using
__builtin_trap() or qualifying pointer with 'volatile'
Since this indirection is done relative to the fs or gs segment, to
retrieve thread-specific data, it is an exception to the rule.
Therefore, add a volatile qualifier to tell the compiler we really want
to dereference a zero address.
MFC after: 1 week
Modified:
head/lib/libthr/arch/amd64/include/pthread_md.h
head/lib/libthr/arch/i386/include/pthread_md.h
Modified: head/lib/libthr/arch/amd64/include/pthread_md.h
==============================================================================
--- head/lib/libthr/arch/amd64/include/pthread_md.h Thu Dec 15 17:54:23
2011 (r228535)
+++ head/lib/libthr/arch/amd64/include/pthread_md.h Thu Dec 15 19:42:25
2011 (r228536)
@@ -71,7 +71,7 @@ struct tcb {
u_long __i; \
__asm __volatile("movq %%fs:%1, %0" \
: "=r" (__i) \
- : "m" (*(u_long *)(__tcb_offset(name)))); \
+ : "m" (*(volatile u_long *)(__tcb_offset(name)))); \
__result = (__tcb_type(name))__i; \
\
__result; \
Modified: head/lib/libthr/arch/i386/include/pthread_md.h
==============================================================================
--- head/lib/libthr/arch/i386/include/pthread_md.h Thu Dec 15 17:54:23
2011 (r228535)
+++ head/lib/libthr/arch/i386/include/pthread_md.h Thu Dec 15 19:42:25
2011 (r228536)
@@ -70,7 +70,7 @@ struct tcb {
u_int __i; \
__asm __volatile("movl %%gs:%1, %0" \
: "=r" (__i) \
- : "m" (*(u_int *)(__tcb_offset(name)))); \
+ : "m" (*(volatile u_int *)(__tcb_offset(name)))); \
__result = (__tcb_type(name))__i; \
\
__result; \
_______________________________________________
svn-src-head@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
