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fix Issue 15672 - Casting from void[] to T[] is erroneously considere… #5876

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merged 1 commit into from
Jun 27, 2016
Merged

fix Issue 15672 - Casting from void[] to T[] is erroneously considere… #5876

merged 1 commit into from
Jun 27, 2016

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WalterBright
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Fix Bugzilla Description
✓ 15672 Casting from void[] to T[] is erroneously considered @safe

@WalterBright WalterBright force-pushed the fix15672 branch 2 times, most recently from fc907f8 to f3e50be Compare June 19, 2016 05:56
@PetarKirov
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LGTM

BTW, with all those @safe fixes, does the spec need to be updated, or you're just fixing the compiler to follow the spec more closely? Anyway it would be helpful if you put @safe label on such PRs for future reference.

@WalterBright WalterBright mentioned this pull request Jun 19, 2016
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@WalterBright
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Blocked by dlang/phobos#4438

@WalterBright
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When all the safety fixed are in, I'll review the spec and make sure it is congruent.

@andralex
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Actually this is excessive. Casting from void[] to T[] is @safe so long as T has no indirections. Size and alignment are checked dynamically anyway, and if T has no indirections scrambled data won't cause unsafe behavior.

@WalterBright
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Casting from void[] to T[] is @safe so long as T has no indirections

Surprisingly, it is not, as the bugzilla issue shows. The problem comes from an array of pointers being cast to void[], then the void[] is cast to int[], then ints are stored there, then the original array of pointers now has arbitrary pointers in it.

@andralex
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blurgh thx

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Auto-merge toggled on

@andralex andralex merged commit 5ca4b33 into dlang:master Jun 27, 2016
@WalterBright WalterBright deleted the fix15672 branch June 27, 2016 01:59
@PetarKirov PetarKirov mentioned this pull request Nov 4, 2016
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PetarKirov added a commit to PetarKirov/D-YAML that referenced this pull request Nov 4, 2016
@PetarKirov
Fix compilation with DMD 2.072
1a811f4 
The following DMD PRs added more rigorous safety checks directly
affecting this project:
* dlang/dmd#5852 (fix Issue 15399 - unaligned pointers are not
  `@safe`) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/emitter.d#L1011

* dlang/dmd#5940 (Unions may break immutability / unions with
  pointers are un-`@safe` ) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/event.d#L230

* dlang/dmd#5876 (Casting from `void[]` to `T[]` is erroneously
  considered `@safe`) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/loader.d#L186

* dlang/dmd#5860 (array.ptr in @safe code may point past end
  of array) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/zerostring.d#L35
@PetarKirov PetarKirov mentioned this pull request Nov 4, 2016
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PetarKirov added a commit to PetarKirov/D-YAML that referenced this pull request Nov 4, 2016
@PetarKirov
Fix compilation with DMD 2.072.0
8d5b75b 
The following DMD PRs added more rigorous safety checks directly
affecting this project:
* dlang/dmd#5852 (fix Issue 15399 - unaligned pointers are not
  `@safe`) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/emitter.d#L1011

* dlang/dmd#5940 (Unions may break immutability / unions with
  pointers are un-`@safe` ) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/event.d#L230

* dlang/dmd#5876 (Casting from `void[]` to `T[]` is erroneously
  considered `@safe`) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/loader.d#L186

* dlang/dmd#5860 (array.ptr in @safe code may point past end
  of array) - triggered at line:
  https://github.com/kiith-sa/D-YAML/blob/v0.5.3/source/dyaml/zerostring.d#L35
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@WalterBright @dlang-bot @PetarKirov @andralex