Re: [PATCH] Warn for dangerous use of omitted middle operand in ?:

[Paolo Bonzini <bonzini at gnu dot org>]

> +/* Warn for A ?: C expressions (with B omitted) where A is a boolean
> +   expression, because B will always be true. */
> +
> +void
> +warn_for_omitted_condop (location_t location, tree cond)
> +{
> +  enum tree_code code = TREE_CODE (cond);
> +
> +  if (!warn_parentheses)
> +    return;
> +  if (TREE_CODE_CLASS (code) == tcc_comparison
> +      || code == TRUTH_ANDIF_EXPR
> +      || code == TRUTH_ORIF_EXPR
> +      || code == TRUTH_AND_EXPR
> +      || code == TRUTH_XOR_EXPR
> +      || code == TRUTH_OR_EXPR
> +      || code == TRUTH_NOT_EXPR)
> +    {
> +      warning_at (location, OPT_Wparentheses,
> +		"the omitted middle operand in ?: will always be %<true%>, "
> +		"suggest explicit middle operand");
> +    }
> +}

As a follow up, if the else-branch is a comparison too you could warn as

    "the omitted middle operand in ?: will always be %<true%>, "
    "suggest using || instead of ?:"

Paolo