TREE_STRING_LENGTH is the size of the character array, not the string.
ONLY_VALUE should be non-zero if the result is not going to be emitted
- into the instruction stream and zero if it si going to be expanded.
+ into the instruction stream and zero if it is going to be expanded.
E.g. with i++ ? "foo" : "bar", if ONLY_VALUE is non-zero, constant 3
is returned, otherwise NULL, since
len = c_strlen (src, 1); if (len) expand_expr (len, ...); would not