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libstdc++: Fix std::format for pointers [PR110239]

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The formatter for pointers was casting to uint64_t which sign extends a
32-bit pointer and produces a value that won't fit in the provided
buffer. Cast to uintptr_t instead.

There was also a bug in the __parse_integer helper when converting a
wide string to a narrow string in order to use std::from_chars on it.
The function would always try to read 32 characters, even if the format
string was shorter than that. Fix that bug, and remove the constexpr
implementation of __parse_integer by just using __from_chars_alnum
instead of from_chars, because that's usable in constexpr even in
C++20.

libstdc++-v3/ChangeLog:

	PR libstdc++/110239
	* include/std/format (__format::__parse_integer): Fix buffer
	overflow for wide chars.
	(formatter<const void*, C>::format): Cast to uintptr_t instead
	of uint64_t.
	* testsuite/std/format/string.cc: Test too-large widths.

(cherry picked from commit 3bb9f9329c378934541ae4cff9977b7487e97cf0)
This commit is contained in:
Jonathan Wakely
2023-06-26 14:46:46 +01:00
parent ae7cdc8c0f
commit 2d40cd2f19
2 changed files with 15 additions and 23 deletions
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libstdc++-v3/include/std/format
+10 -23
View File
@@ -269,39 +269,26 @@ namespace __format
if (__first == __last)
__builtin_unreachable();
// TODO: use this loop unconditionally?
// Most integers used for arg-id, width or precision will be small.
if (is_constant_evaluated())
{
auto __next = __first;
unsigned short __val = 0;
while (__next != __last && '0' <= *__next && *__next <= '9')
{
__val = (__val * 10) + (*__next - '0'); // TODO check overflow?
++__next;
}
if (__next == __first)
return {0, nullptr};
return {__val, __next};
}
unsigned short __val = 0;
if constexpr (is_same_v<_CharT, char>)
{
auto [ptr, ec] = std::from_chars(__first, __last, __val);
if (ec == errc{})
return {__val, ptr};
return {0, nullptr};
const auto __start = __first;
unsigned short __val = 0;
// N.B. std::from_chars is not constexpr in C++20.
if (__detail::__from_chars_alnum<true>(__first, __last, __val, 10)
&& __first != __start) [[likely]]
return {__val, __first};
}
else
{
unsigned short __val = 0;
constexpr int __n = 32;
char __buf[__n]{};
for (int __i = 0; __i < __n && __first != __last; ++__i)
for (int __i = 0; __i < __n && (__first + __i) != __last; ++__i)
__buf[__i] = __first[__i];
auto [__v, __ptr] = __format::__parse_integer(__buf, __buf + __n);
return {__v, __first + (__ptr - __buf)};
}
return {0, nullptr};
}
template<typename _CharT>
@@ -2118,7 +2105,7 @@ namespace __format
typename basic_format_context<_Out, _CharT>::iterator
format(const void* __v, basic_format_context<_Out, _CharT>& __fc) const
{
auto __u = reinterpret_cast<__UINT64_TYPE__>(__v);
auto __u = reinterpret_cast<__UINTPTR_TYPE__>(__v);
char __buf[2 + sizeof(__v) * 2];
auto [__ptr, __ec] = std::to_chars(__buf + 2, std::end(__buf),
__u, 16);
libstdc++-v3/testsuite/std/format/string.cc
+5
View File
@@ -121,6 +121,11 @@ test_format_spec()
// Invalid presentation types for strings.
VERIFY( ! is_format_string_for("{:S}", "str") );
VERIFY( ! is_format_string_for("{:d}", "str") );
// Maximum integer value supported for widths and precisions is USHRT_MAX.
VERIFY( is_format_string_for("{:65535}", 1) );
VERIFY( ! is_format_string_for("{:65536}", 1) );
VERIFY( ! is_format_string_for("{:9999999}", 1) );
}
int main()