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| author | Jonathan Wakely <jwakely@redhat.com> | 2021-09-15 21:40:20 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2021-09-16 22:59:47 +0100 |
| commit | 9d813ddd978aff75001d53fe55ff15e9167bb4d0 (patch) | |
| tree | 94e6128801543a537a63b461b0a4056336a9ede7 | |
| parent | 869107c9c9752c9a53cdb06179c1e6be6d2e5f44 (diff) | |
| download | gcc-9d813ddd978aff75001d53fe55ff15e9167bb4d0.zip gcc-9d813ddd978aff75001d53fe55ff15e9167bb4d0.tar.gz gcc-9d813ddd978aff75001d53fe55ff15e9167bb4d0.tar.bz2 | |
libstdc++: Add noexcept to std::to_string overloads that don't allocate
When the values is guaranteed to fit in the SSO buffer we know the
string won't allocate, so the function can be noexcept. For 32-bit
integers, we know they need no more than 9 bytes (or 10 with a minus
sign) and the SSO buffer is 15 bytes.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
(to_string): Add noexcept if the type width is 32 bits or less.
| -rw-r--r-- | libstdc++-v3/include/bits/basic_string.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index b61fe05..24c454d 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -3718,6 +3718,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(int __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { const bool __neg = __val < 0; const unsigned __uval = __neg ? (unsigned)~__val + 1u : __val; @@ -3729,6 +3732,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(unsigned __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { string __str(__detail::__to_chars_len(__val), '\0'); __detail::__to_chars_10_impl(&__str[0], __str.size(), __val); @@ -3737,6 +3743,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(long __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { const bool __neg = __val < 0; const unsigned long __uval = __neg ? (unsigned long)~__val + 1ul : __val; @@ -3748,6 +3757,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(unsigned long __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { string __str(__detail::__to_chars_len(__val), '\0'); __detail::__to_chars_10_impl(&__str[0], __str.size(), __val); |