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(internal_build_compound_expr): Warn if LHS of comma expression has no side effects... 

(internal_build_compound_expr): Warn if LHS of comma expression has no
side effects, or computes value which is not used.

From-SVN: r9264
This commit is contained in:
Richard Kenner 1995-03-30 18:21:34 -05:00
parent 515a7242ff
commit 0e7c47fabe
1 changed files with 22 additions and 4 deletions
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26
gcc/c-typeck.c
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@ -3478,10 +3478,28 @@ internal_build_compound_expr (list, first_p)
rest = internal_build_compound_expr (TREE_CHAIN (list), FALSE);
/* When pedantic, a compound expression can be neither an lvalue
nor an integer constant expression. */
if (! TREE_SIDE_EFFECTS (TREE_VALUE (list)) && ! pedantic)
return rest;
if (! TREE_SIDE_EFFECTS (TREE_VALUE (list)))
{
/* The left-hand operand of a comma expression is like an expression
statement: with -W or -Wunused, we should warn if it doesn't have
any side-effects, unless it was explicitly cast to (void). */
if ((extra_warnings || warn_unused)
&& ! (TREE_CODE (TREE_VALUE (list)) == CONVERT_EXPR
&& TREE_TYPE (TREE_VALUE (list)) == void_type_node))
warning ("left-hand operand of comma expression has no effect");
/* When pedantic, a compound expression can be neither an lvalue
nor an integer constant expression. */
if (! pedantic)
return rest;
}
/* With -Wunused, we should also warn if the left-hand operand does have
side-effects, but computes a value which is not used. For example, in
`foo() + bar(), baz()' the result of the `+' operator is not used,
so we should issue a warning. */
else if (warn_unused)
warn_if_unused_value (TREE_VALUE (list));
return build (COMPOUND_EXPR, TREE_TYPE (rest), TREE_VALUE (list), rest);
}