On Tue, 1 Sep 2026, Martin Uecker wrote:
> c: split -Wwrite-strings into a proper warning and a flag [PR61579]
>
> This adds a new flag -fconst-string-literals that toggles whether
> string literals are const-qualified or not. The warning -Wwrite-strings
> is reimplemented as warning that warns whenever a string literal is
> implicitely converted to a pointer to a non-const-qualified character
> type independently on whether the string literal is actually const
> qualified or not. For C++ and with -fconst-string-literals also C,
> the warning is activated by default.
I think -Wwrite-strings has been around for so long with its current
semantics that it should be considered a semantic option that changes the
type of string literals, despite its -W name; anything that does not
change the type should be named differently. (This does not prevent
giving more precise diagnostics with -Wwrite-strings in the specific case
of string literals, as long as they are consistent with still having
const-qualified types - for example, as long as they remain pedwarns and
typeof produces the const-qualified types.)
> +/* Test whether EXPR is a string literal. */
> +
> +static bool
> +string_literal_p (tree expr)
I suppose it's hard to get a c_expr, or information obtained from a
c_expr, in the places where this information is needed? Since checking
original_code against STRING_CST would seem cleaner than trying to
reconstruct the information later.
> + expr = TREE_OPERAND(expr, 0);
Missing space before '('.
> @@ -8841,6 +8892,7 @@ convert_for_assignment (location_t location, location_t
> expr_loc, tree type,
> /* Opaque pointers are treated like void pointers. */
> is_opaque_pointer = vector_targets_convertible_p (ttl, ttr);
>
> +
> /* The Plan 9 compiler permits a pointer to a struct to be
> automatically converted into a pointer to an anonymous field
> within the struct. */
Why the extra blank line?
> @@ -9038,7 +9090,7 @@ convert_for_assignment (location_t location, location_t
> expr_loc, tree type,
> and vice versa; otherwise, targets must be the same.
> Meanwhile, the lhs target must have all the qualifiers of the rhs. */
> if ((VOID_TYPE_P (ttl) && !TYPE_ATOMIC (ttl))
> - || (VOID_TYPE_P (ttr) && !TYPE_ATOMIC (ttr))
> + || (VOID_TYPE_P (ttr) && !TYPE_ATOMIC (ttr)) // FIXME
A FIXME isn't helpful without saying what's wrong that needs to be fixed.
--
Joseph S. Myers
[email protected]
