Re: [PATCH 1/2] Fix new -Wparentheses warnings encountered during bootstrap

[Bernd Schmidt]

On 03/31/2016 10:53 PM, Patrick Palka wrote:
This patch fixes the new -Wparentheses warnings (implemented by the
subsequent patch) that are encountered during bootstrap:
/home/patrick/code/gcc/gcc/omp-low.c: In function ‘void 
scan_sharing_clauses(tree, omp_context*, bool)’:
/home/patrick/code/gcc/gcc/omp-low.c:2381:6: error: suggest explicit braces to 
avoid ambiguous ‘else’ [-Werror=parentheses]
    if (scan_array_reductions)
       ^
/home/patrick/code/gcc/gcc/gimplify.c: In function ‘gimple* 
gimplify_omp_ordered(tree, gimple_seq)’:
/home/patrick/code/gcc/gcc/gimplify.c:9880:6: error: suggest explicit braces to 
avoid ambiguous ‘else’ [-Werror=parentheses]
    if (gimplify_omp_ctxp)
       ^
In file included from /home/patrick/code/gcc/gcc/cp/optimize.c:25:0:
/home/patrick/code/gcc/gcc/cp/optimize.c: In function ‘void 
populate_clone_array(tree, tree_node**)’:
/home/patrick/code/gcc/gcc/cp/cp-tree.h:2529:6: error: suggest explicit braces 
to avoid ambiguous ‘else’ [-Werror=parentheses]
    if (TREE_CODE (FN) == FUNCTION_DECL   \
       ^
/home/patrick/code/gcc/gcc/cp/optimize.c:222:3: note: in expansion of macro 
‘FOR_EACH_CLONE’
    FOR_EACH_CLONE (clone, fn)
    ^~~~~~~~~~~~~~
/home/patrick/code/gcc/gcc/fortran/openmp.c: In function ‘gfc_omp_udr* 
gfc_find_omp_udr(gfc_namespace*, const char*, gfc_typespec*)’:
/home/patrick/code/gcc/gcc/fortran/openmp.c:177:10: error: suggest explicit 
braces to avoid ambiguous ‘else’ [-Werror=parentheses]
        if (st != NULL)
           ^

In each case I think the warning is harmless since the indentation of
the code in question corresponds to how the "else" is actually parsed
so I fixed each case simply by enclosing the entire body of the outer
"if" in braces.

The FOR_EACH_CLONE change resolves the cp/optimize.c warning.  It
adjusts the layout of the macro from

   if (p)
     for (...)

to

   if (!p)
     ;
   else for (...)

so that an "else" encountered in the body of the for-statement can no
longer possibly bind to the outer "if (p)" conditional.

Is this OK to commit after bootstrap + regtesting?

I think this is OK, now or in stage1 depending on whether the warning 
improvements go in now or later.

I see a patch for the C++ side fixing the warning, do you also intend to 
do C?


Bernd