C++26: Std:Is_within_lifetime

\u003ch2\u003eC++26: Std:Is_within_lifetime\u003c/h2\u003e \u003cp\u003e Hāʻawi kēia ʻatikala i nā ʻike koʻikoʻi a me ka ʻike e pili ana i kāna kumuhana, e kōkua ana i ka kaʻana like ʻana a me ka ʻike.\u003c/p\u003e \u003ch3\u003eKuhi Lawelawe\u003c/h3\u003e \u003cp\u003e Hiki i ka poʻe heluhelu ke manaʻo e loaʻa:\u003c/p\u003e \u003cul\u003e \u003cli\u003e Hoʻomaopopo hohonu i ke kumuhana\u003c/li\u003e \u003cli\u003e Nā noi kūpono a me ka pili honua maoli\u003c/li\u003e \u003cli\u003eNā kuanaʻike loea a me ka nānā ʻana\u003c/li\u003e \u003cli\u003e ʻike hou ʻia e pili ana i nā hanana o kēia manawa\u003c/li\u003e \u003c/ul\u003e \u003ch3\u003e Manao Waiwai\u003c/h3\u003e \u003cp\u003e ʻO nā maʻiʻo kūpono e like me kēia e kōkua i ke kūkulu ʻana i ka ʻike a me ka paipai ʻana i ka hoʻoholo hoʻoholo ʻike ma nā wahi like ʻole.\u003c/p\u003e

Nīnau pinepine

He aha ia std::is_within_lifetime a no ke aha i hoʻokomo ʻia ai ma C++26?

std::is_within_lifetime he hōʻuluʻulu manawa hou i hoʻokomo ʻia ma C++26 e hoʻoholo ai inā pili ka kuhikuhi i kekahi mea i kēia manawa i loko o kona ola i ka wā o ka loiloi mau. Ua hoʻolauna ʻia e hoʻoponopono i kahi āpau lōʻihi i ka papahana constexpr, kahi i loaʻa ʻole ai i nā mea hoʻomohala ke ala palekana a hiki ʻole ke ʻike i ke komo ʻana i nā kuhikuhi i ka wā o ka helu ʻana i ka manawa, e hiki ai i nā code constexpr ʻoi aku ka ikaika a me ka ʻike ʻole me ka hilinaʻi ʻole i ke ʻano i wehewehe ʻole ʻia.

Pehea ka ʻokoʻa std::is_within_lifetime me nā hōʻoia kūpono o nā kuhikuhi?

ʻAʻole like me ka nānā ʻana i ka wā holo e like me ka hoʻohālikelike null pointer a i ʻole nā mea hana hoʻomaʻemaʻe, std::is_within_lifetime e hana wale ana i loko o nā pōʻaiapili loiloi mau. ʻAʻole ia he hana runtime - ʻaʻole hiki ke kapa ʻia ma ke code runtime maʻamau. Hoʻokaʻawale kēia i nā mea hana e like me AddressSanitizer, e hana ana i ka post-compilation. Hāʻawi ia i ka mea hōʻuluʻulu iā ia iho ka mana e pane i nā nīnau o ke ola, e hana ana i constexpr union-based type punning a me nā ʻano like ʻole i wehewehe maikaʻi ʻia a hiki ke nānā ʻia.

He aha nā hihia hoʻohana kūpono a std::is_within_lifetime wehe i nā mea hoʻomohala C++?

ʻO ka hoʻohana koke ʻana i ka constexpr-friendly std::optional a me std::variant me ka ʻole hacks. Hiki i nā mea hoʻomohala ke nānā pono i kēia manawa inā kūpono ka lālā ikaika o kahi uniona i ka wā o ka loiloi manawa hōʻuluʻulu. No nā hui e kūkulu nei i nā mea hana C++ hou, nā hale waihona puke, a i ʻole nā paepae - e like me ka hoʻohui ʻana i nā kahe hana hoʻomohala ma o Mewayz (207 modules, e hoʻomaka ana ma $19/mo) - ʻo kēia hiʻohiʻona e hōʻemi nui i nā pōʻino o ke ʻano i wehewehe ʻole ʻia i nā codebase kaumaha kaumaha.

Ke kākoʻo ʻia nei ka std::is_within_lifetime i nā mea hoʻopili nui a me nā hiʻohiʻona C++26 ʻē aʻe?

Ma ka hoʻomaka ʻana o ka makahiki 2026, ke hoʻomau nei ke kākoʻo o ka mea hōʻuluʻulu no std::is_within_lifetime. Loaʻa iā GCC a me Clang ke kākoʻo hoʻokolohua C++26 ma o nā hae -std=c++26, me ka loaʻa ʻana o nā hiʻohiʻona hapa. Ke holomua nei ʻo MSVC ma kāna palapala alanui C++26. Manaʻo ʻia nā mea hoʻomohala e nānā i nā macros hoʻāʻo hiʻohiʻona compiler (__cpp_lib_is_within_lifetime) ma mua o ka hoʻohana ʻana. Ke noho nei i kēia manawa me ka hoʻonui ʻana i nā mea hana a me ka mālama ʻana i kāu kaiapuni dev - he mea nui nā paepae e like me Mewayz ma o kā lākou 207 modules - he mea nui.