On 07/31/2018 07:38 AM, Jason Merrill wrote:
On Tue, Jul 31, 2018 at 9:51 AM, Martin Sebor <mse...@gmail.com> wrote:
The middle-end contains code to determine the lengths of constant
character arrays initialized by string literals. The code is used
in a number of optimizations and warnings.
However, the code is unable to deal with constant arrays initialized
using the braced initializer syntax, as in
const char a[] = { '1', '2', '\0' };
The attached patch extends the C and C++ front-ends to convert such
initializers into a STRING_CST form.
The goal of this work is to both enable existing optimizations for
such arrays, and to help detect bugs due to using non-nul terminated
arrays where nul-terminated strings are expected. The latter is
an extension of the GCC 8 _Wstringop-overflow and
-Wstringop-truncation warnings that help detect or prevent reading
past the end of dynamically created character arrays. Future work
includes detecting potential past-the-end reads from uninitialized
local character arrays.
&& TYPE_MAIN_VARIANT (TREE_TYPE (valtype)) == char_type_node)
Why? Don't we want this for other character types as well?
It suppresses narrowing warnings for things like
signed char a[] = { 0xff };
(there are a couple of tests that exercise this).
At the same time, STRING_CST is supposed to be able to represent
strings of any integer type so there should be a way to make it
work. On the flip side, recent discussions of changes in this
area suggest there may be bugs in the wide character handling of
STRING_CST so those would need to be fixed before relying on it
for robust support.
In any case, if you have a suggestion for how to make it work for
at least the narrow character types I'll adjust the patch.
Martin
