Re: [PATCH 1/2] libstdc++: case-sensitivity in hexfloat std::from_chars [PR105441]

[Jonathan Wakely <jwakely@redhat.com>]

On Sun, 1 May 2022 at 19:22, Patrick Palka via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> The hexfloat parser for binary32/64 added in r12-6645-gcc3bf3404e4b1c
> overlooked that the exponent part can also begin with an uppercase 'P'.
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk/11, and possibly the
> 12 branch now for 12.1?

OK for trunk, and as it's a regression since gcc-11 I'd recommend
release manager approval for 12.1 as well, but it's the RMs call.



>
>         PR libstdc++/105441
>
> libstdc++-v3/ChangeLog:
>
>         * src/c++17/floating_from_chars.cc (__floating_from_chars_hex):
>         Also accept 'P' as the start of the exponent.
>         * testsuite/20_util/from_chars/7.cc: Add corresponding testcase.
> ---
>  libstdc++-v3/src/c++17/floating_from_chars.cc  | 2 +-
>  libstdc++-v3/testsuite/20_util/from_chars/7.cc | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc b/libstdc++-v3/src/c++17/floating_from_chars.cc
> index 13de1e346ab..e7f3a58cf18 100644
> --- a/libstdc++-v3/src/c++17/floating_from_chars.cc
> +++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
> @@ -664,7 +664,7 @@ namespace
>
>      // Parse the written exponent.
>      int written_exponent = 0;
> -    if (first != last && *first == 'p')
> +    if (first != last && (*first == 'p' || *first == 'P'))
>        {
>         // Tentatively consume the 'p' and try to parse a decimal number.
>         const char* const fallback_first = first;
> diff --git a/libstdc++-v3/testsuite/20_util/from_chars/7.cc b/libstdc++-v3/testsuite/20_util/from_chars/7.cc
> index 2a78c7441e2..1aa9b230531 100644
> --- a/libstdc++-v3/testsuite/20_util/from_chars/7.cc
> +++ b/libstdc++-v3/testsuite/20_util/from_chars/7.cc
> @@ -96,6 +96,7 @@ constexpr testcase testcases[] = {
>    { "1p-1", 4, {}, 0x1p-1 },
>    { "0", 1, {}, 0.0 },
>    { "A", 1, {}, 0xA },
> +  { "1.ABCDEFP+10", 12, {}, 0x1.ABCDEFP+10 },
>    { "-1", 2, {}, -1.0 },
>    { "-0", 2, {}, -0.0 },
>    { "42", 2, {}, 0x42p0 },
> --
> 2.36.0.44.g0f828332d5
>