[Openmp-dev] variable 'new_value' is used uninitialized whenever 'if' condition is false

[Jack Howarth]

Jonathan,
      Are the warnings of the form...

/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2035:1:
warning: variable 'new_value' is used uninitialized whenever 'if'
condition is false
      [-Wsometimes-uninitialized]
MIN_MAX_COMPXCHG_CPT( fixed1,  max_cpt, char,        8, <,
KMP_ARCH_X86 ) // __kmpc_atomic_fixed1_max_cpt
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2028:9:
note: expanded from macro 'MIN_MAX_COMPXCHG_CPT'
        GOMP_MIN_MAX_CRITSECT_CPT(OP,GOMP_FLAG)                            \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:1984:9:
note: expanded from macro 'GOMP_MIN_MAX_CRITSECT_CPT'
        MIN_MAX_CRITSECT_CPT( OP, 0 );                                     \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:1968:10:
note: expanded from macro 'MIN_MAX_CRITSECT_CPT'
    if ( *lhs OP rhs ) {                 /* still need actions? */         \
         ^~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2035:1:
note: uninitialized use occurs here
MIN_MAX_COMPXCHG_CPT( fixed1,  max_cpt, char,        8, <,
KMP_ARCH_X86 ) // __kmpc_atomic_fixed1_max_cpt
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2028:9:
note: expanded from macro 'MIN_MAX_COMPXCHG_CPT'
        GOMP_MIN_MAX_CRITSECT_CPT(OP,GOMP_FLAG)                            \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:1984:9:
note: expanded from macro 'GOMP_MIN_MAX_CRITSECT_CPT'
        MIN_MAX_CRITSECT_CPT( OP, 0 );                                     \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:1977:12:
note: expanded from macro 'MIN_MAX_CRITSECT_CPT'
    return new_value;                                                      \
           ^~~~~~~~~
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2035:1:
note: remove the 'if' if its condition is always true
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2028:9:
note: expanded from macro 'MIN_MAX_COMPXCHG_CPT'
        GOMP_MIN_MAX_CRITSECT_CPT(OP,GOMP_FLAG)                            \
        ^
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:1984:9:
note: expanded from macro 'GOMP_MIN_MAX_CRITSECT_CPT'
        MIN_MAX_CRITSECT_CPT( OP, 0 );                                     \
        ^
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:1968:5:
note: expanded from macro 'MIN_MAX_CRITSECT_CPT'
    if ( *lhs OP rhs ) {                 /* still need actions? */         \
    ^
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2035:41:
note: variable 'new_value' is declared here
MIN_MAX_COMPXCHG_CPT( fixed1,  max_cpt, char,        8, <,
KMP_ARCH_X86 ) // __kmpc_atomic_fixed1_max_cpt
                                        ^
/sw/src/fink.build/llvm37-3.7.0-100/llvm-3.7.0.src/projects/openmp/runtime/src/kmp_atomic.c:2026:5:
note: expanded from macro 'MIN_MAX_COMPXCHG_CPT'
    TYPE new_value, old_value;                                             \
    ^

significant? These seem to be generated from the macro definition...

#define MIN_MAX_COMPXCHG_CPT(TYPE_ID,OP_ID,TYPE,BITS,OP,GOMP_FLAG)         \
ATOMIC_BEGIN_CPT(TYPE_ID,OP_ID,TYPE,TYPE)                                  \
    TYPE new_value, old_value;                                             \
    if ( *lhs OP rhs ) {                                                   \
        GOMP_MIN_MAX_CRITSECT_CPT(OP,GOMP_FLAG)                            \
        MIN_MAX_CMPXCHG_CPT(TYPE,BITS,OP)                                  \
    }                                                                      \
    return *lhs;                                                           \
}

        Jack