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Modify SCM_UNPACK type check to avoid warnings in clang.

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* libguile/tags.h (SCM_UNPACK): Change (*(SCM*)0=(x)) to
  (*(volatile SCM *)0=(x)), to avoid null-dereference warnings
  from clang.  Reported by Shane Celis <shane.celis@gmail.com>.
This commit is contained in:
Mark H Weaver 2013-07-18 14:10:43 -04:00
parent fe51c7b3e0
commit 824b9ad8b7
1 changed files with 3 additions and 2 deletions
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libguile/tags.h
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@ -87,14 +87,15 @@ typedef union SCM { struct { scm_t_bits n; } n; } SCM;
The 0?: constructions makes sure that the code is never executed, The 0?: constructions makes sure that the code is never executed,
and that there is no performance hit. However, the alternative is and that there is no performance hit. However, the alternative is
compiled, and does generate a warning when used with the wrong compiled, and does generate a warning when used with the wrong
pointer type. pointer type. We use a volatile pointer type to avoid warnings
from clang.
The Tru64 and ia64-hp-hpux11.23 compilers fail on `case (0?0=0:x)' The Tru64 and ia64-hp-hpux11.23 compilers fail on `case (0?0=0:x)'
statements, so for them type-checking is disabled. */ statements, so for them type-checking is disabled. */
#if defined __DECC || defined __HP_cc #if defined __DECC || defined __HP_cc
# define SCM_UNPACK(x) ((scm_t_bits) (x)) # define SCM_UNPACK(x) ((scm_t_bits) (x))
#else #else
# define SCM_UNPACK(x) ((scm_t_bits) (0? (*(SCM*)0=(x)): x)) # define SCM_UNPACK(x) ((scm_t_bits) (0? (*(volatile SCM *)0=(x)): x))
#endif #endif
/* /*