master

GGitHub[libc++] Ensure that std::expected has no tail padding (#69673)

4f469053创建于 2024年1月22日历史提交

文件	最后提交记录	最后更新时间
assign.copy.pass.cpp	[libc++] Ensure that std::expected has no tail padding (#69673) Currently std::expected can have some padding bytes in its tail due to [[no_unique_address]]. Those padding bytes can be used by other objects. For example, in the current implementation: sizeof(std::expected<std::optional<int>, bool>) == sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) As a result, the data layout of an std::expected<std::expected<std::optional<int>, bool>, bool> can look like this: +-- optional "has value" flag | +--padding /---int---\ | | 00 00 00 00 01 00 00 00 | | | +- "outer" expected "has value" flag | +- expected "has value" flag This is problematic because emplace()ing the "inner" expected can not only overwrite the "inner" expected "has value" flag (issue #68552) but also the tail padding where other objects might live. This patch fixes the problem by ensuring that std::expected has no tail padding, which is achieved by conditional usage of [[no_unique_address]] based on the tail padding that this would create. This is an ABI breaking change because the following property changes: sizeof(std::expected<std::optional<int>, bool>) < sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) Before the change, this relation didn't hold. After the change, the relation does hold, which means that the size of std::expected in these cases increases after this patch. The data layout will change in the following cases where tail padding can be reused by other objects: class foo : std::expected<std::optional<int>, bool> { bool b; }; or using [[no_unique_address]]: struct foo { [[no_unique_address]] std::expected<std::optional<int>, bool> e; bool b; }; The vendor communication is handled in #70820. Fixes: #70494 Co-authored-by: philnik777 <nikolasklauser@berlin.de> Co-authored-by: Louis Dionne <ldionne.2@gmail.com>	2 年前
assign.move.pass.cpp	[libc++] Ensure that std::expected has no tail padding (#69673) Currently std::expected can have some padding bytes in its tail due to [[no_unique_address]]. Those padding bytes can be used by other objects. For example, in the current implementation: sizeof(std::expected<std::optional<int>, bool>) == sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) As a result, the data layout of an std::expected<std::expected<std::optional<int>, bool>, bool> can look like this: +-- optional "has value" flag | +--padding /---int---\ | | 00 00 00 00 01 00 00 00 | | | +- "outer" expected "has value" flag | +- expected "has value" flag This is problematic because emplace()ing the "inner" expected can not only overwrite the "inner" expected "has value" flag (issue #68552) but also the tail padding where other objects might live. This patch fixes the problem by ensuring that std::expected has no tail padding, which is achieved by conditional usage of [[no_unique_address]] based on the tail padding that this would create. This is an ABI breaking change because the following property changes: sizeof(std::expected<std::optional<int>, bool>) < sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) Before the change, this relation didn't hold. After the change, the relation does hold, which means that the size of std::expected in these cases increases after this patch. The data layout will change in the following cases where tail padding can be reused by other objects: class foo : std::expected<std::optional<int>, bool> { bool b; }; or using [[no_unique_address]]: struct foo { [[no_unique_address]] std::expected<std::optional<int>, bool> e; bool b; }; The vendor communication is handled in #70820. Fixes: #70494 Co-authored-by: philnik777 <nikolasklauser@berlin.de> Co-authored-by: Louis Dionne <ldionne.2@gmail.com>	2 年前
assign.unexpected.copy.pass.cpp	[libc++] Ensure that std::expected has no tail padding (#69673) Currently std::expected can have some padding bytes in its tail due to [[no_unique_address]]. Those padding bytes can be used by other objects. For example, in the current implementation: sizeof(std::expected<std::optional<int>, bool>) == sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) As a result, the data layout of an std::expected<std::expected<std::optional<int>, bool>, bool> can look like this: +-- optional "has value" flag | +--padding /---int---\ | | 00 00 00 00 01 00 00 00 | | | +- "outer" expected "has value" flag | +- expected "has value" flag This is problematic because emplace()ing the "inner" expected can not only overwrite the "inner" expected "has value" flag (issue #68552) but also the tail padding where other objects might live. This patch fixes the problem by ensuring that std::expected has no tail padding, which is achieved by conditional usage of [[no_unique_address]] based on the tail padding that this would create. This is an ABI breaking change because the following property changes: sizeof(std::expected<std::optional<int>, bool>) < sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) Before the change, this relation didn't hold. After the change, the relation does hold, which means that the size of std::expected in these cases increases after this patch. The data layout will change in the following cases where tail padding can be reused by other objects: class foo : std::expected<std::optional<int>, bool> { bool b; }; or using [[no_unique_address]]: struct foo { [[no_unique_address]] std::expected<std::optional<int>, bool> e; bool b; }; The vendor communication is handled in #70820. Fixes: #70494 Co-authored-by: philnik777 <nikolasklauser@berlin.de> Co-authored-by: Louis Dionne <ldionne.2@gmail.com>	2 年前
assign.unexpected.move.pass.cpp	[libc++] Ensure that std::expected has no tail padding (#69673) Currently std::expected can have some padding bytes in its tail due to [[no_unique_address]]. Those padding bytes can be used by other objects. For example, in the current implementation: sizeof(std::expected<std::optional<int>, bool>) == sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) As a result, the data layout of an std::expected<std::expected<std::optional<int>, bool>, bool> can look like this: +-- optional "has value" flag | +--padding /---int---\ | | 00 00 00 00 01 00 00 00 | | | +- "outer" expected "has value" flag | +- expected "has value" flag This is problematic because emplace()ing the "inner" expected can not only overwrite the "inner" expected "has value" flag (issue #68552) but also the tail padding where other objects might live. This patch fixes the problem by ensuring that std::expected has no tail padding, which is achieved by conditional usage of [[no_unique_address]] based on the tail padding that this would create. This is an ABI breaking change because the following property changes: sizeof(std::expected<std::optional<int>, bool>) < sizeof(std::expected<std::expected<std::optional<int>, bool>, bool>) Before the change, this relation didn't hold. After the change, the relation does hold, which means that the size of std::expected in these cases increases after this patch. The data layout will change in the following cases where tail padding can be reused by other objects: class foo : std::expected<std::optional<int>, bool> { bool b; }; or using [[no_unique_address]]: struct foo { [[no_unique_address]] std::expected<std::optional<int>, bool> e; bool b; }; The vendor communication is handled in #70820. Fixes: #70494 Co-authored-by: philnik777 <nikolasklauser@berlin.de> Co-authored-by: Louis Dionne <ldionne.2@gmail.com>	2 年前
emplace.pass.cpp	[runtimes] Bump the supported AppleClang version to AppleClang 15 (#67065) AppleClang 15 was released on September 18th and is now stable. Per our policy, we're bumping the supported AppleClang compiler to the latest release. This allows cleaning up the test suite, but most importantly unblocking various other patches that are blocked on bumping the compiler requirements.	2 年前