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June 15, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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 | https://issues.dlang.org/show_bug.cgi?id=19968 --- Comment #1 from Tim <tim.dlang@t-online.de> --- The ABI specifies, that bool are 0 or 1: https://dlang.org/spec/abi.html#basic_types There are multiple options to solve this bug: 1. Make sure @safe code can not create invalid bools. 2. Change the ABI, so all values are valid. This could result in slower code being generated. -- | |||
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ReplyJune 15, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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 | https://issues.dlang.org/show_bug.cgi?id=19968 ag0aep6g <ag0aep6g@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |safe CC| |ag0aep6g@gmail.com -- | |||
June 15, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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 | https://issues.dlang.org/show_bug.cgi?id=19968 timon.gehr@gmx.ch changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |timon.gehr@gmx.ch --- Comment #2 from timon.gehr@gmx.ch --- Note that there is a general problem with `void` initialization, not only of bools but for all data types that have a (possibly implicit) invariant. If @safe code can `void`-initialize a struct with private members, @trusted code can't establish any invariants, which would cripple it. -- | |||
June 15, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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| https://issues.dlang.org/show_bug.cgi?id=19968 --- Comment #3 from timon.gehr@gmx.ch --- Also, the spec currently states: "Undefined Behavior: If a void initialized variable's value is used before it is set, the behavior is undefined." https://dlang.org/spec/declaration.html#void_init Unless this is changed (and I don't see a compelling reason to), there can't be _any_ `void` initialization in @safe code. -- | |||
June 15, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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| https://issues.dlang.org/show_bug.cgi?id=19968 --- Comment #4 from ag0aep6g <ag0aep6g@gmail.com> --- (In reply to timon.gehr from comment #3) > Also, the spec currently states: > > "Undefined Behavior: If a void initialized variable's value is used before it is set, the behavior is undefined." > > https://dlang.org/spec/declaration.html#void_init > > Unless this is changed (and I don't see a compelling reason to), there can't be _any_ `void` initialization in @safe code. That's issue 18016, and Walter has an open PR to resolve it by changing the spec: <https://github.com/dlang/dlang.org/pull/2260>. -- | |||
June 15, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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| https://issues.dlang.org/show_bug.cgi?id=19968 --- Comment #5 from Tim <tim.dlang@t-online.de> --- Maybe even types like ubyte can have the same problem on some architectures. If a parameter is stored in a register, which is bigger than the type, the compiler could assume the value is in the correct range. But an uninitialized variable could result in an uninitialized register. -- | |||
June 17, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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 | https://issues.dlang.org/show_bug.cgi?id=19968 Walter Bright <bugzilla@digitalmars.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bugzilla@digitalmars.com --- Comment #6 from Walter Bright <bugzilla@digitalmars.com> --- (In reply to Tim from comment #5) > Maybe even types like ubyte can have the same problem on some architectures. If a parameter is stored in a register, which is bigger than the type, the compiler could assume the value is in the correct range. But an uninitialized variable could result in an uninitialized register. When registers load a ubyte, and then the whole register is used, there must have been a conversion from ubyte to the larger size first, so I don't think this is an issue. -- | |||
June 17, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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| https://issues.dlang.org/show_bug.cgi?id=19968 --- Comment #7 from Walter Bright <bugzilla@digitalmars.com> --- > Variables of type bool are expected to be 0 or 1. Using void initialization this invariant can be wrong. This can result in memory corruption. That is correct. But I don't think this generalizes to other integer types. -- | |||
June 17, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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| https://issues.dlang.org/show_bug.cgi?id=19968 --- Comment #8 from Walter Bright <bugzilla@digitalmars.com> --- (In reply to Walter Bright from comment #7) > That is correct. But I don't think this generalizes to other integer types. Mainly because the compiler doesn't do bounds checking when indexing by bool and the array size is known to be >= 2. -- | |||
June 18, 2019 [Issue 19968] @safe code can create invalid bools resulting in memory corruption | ||||
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 | https://issues.dlang.org/show_bug.cgi?id=19968 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull --- Comment #9 from Dlang Bot <dlang-bot@dlang.rocks> --- @WalterBright created dlang/dmd pull request #10055 "fix Issue 19968 - @safe code can create invalid bools resulting in me…" fixing this issue: - fix Issue 19968 - @safe code can create invalid bools resulting in memory corruption https://github.com/dlang/dmd/pull/10055 -- | |||
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