Templated _d_arrayshrinkfit implementation #21173
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Thanks for your pull request and interest in making D better, @yashjha123! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please see CONTRIBUTING.md for more information. If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment. Bugzilla referencesYour PR doesn't reference any Bugzilla issue. If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog. Testing this PR locallyIf you don't have a local development environment setup, you can use Digger to test this PR: dub run digger -- build "master + dmd#21173" |
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| @safe unittest | ||
| { | ||
| struct S | ||
| { | ||
| float f = 1.0; | ||
| } | ||
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| int[] arr; | ||
| _d_arraysetlengthTImpl!(typeof(arr))._d_arraysetlengthT(arr, 16); | ||
| assert(arr.length == 16); | ||
| foreach (int i; arr) | ||
| assert(i == int.init); | ||
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| shared S[] arr2; | ||
| _d_arraysetlengthTImpl!(typeof(arr2))._d_arraysetlengthT(arr2, 16); | ||
| assert(arr2.length == 16); | ||
| foreach (s; arr2) | ||
| assert(s == S.init); | ||
| } |
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Why did you add this test? It's about _d_arraysetlengthT.
| ti = `TypeInfo` of array type | ||
| arr = array to shrink. Its `.length` is element length, not byte length, despite `void` type | ||
| */ | ||
| void _d_arrayshrinkfit(T)(void[] arr) nothrow |
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| void _d_arrayshrinkfit(T)(void[] arr) nothrow | |
| void _d_arrayshrinkfit(T)(T[] arr) @trusted |
The compiler infers pure, @safe and nothrow for templates. But hooks are almost never safe, so mark them as @trusted.
| // invalid situation, or no change. | ||
| return; | ||
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| static if (is(T == struct) && hasElaborateDestructor!T) |
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| static if (is(T == struct) && hasElaborateDestructor!T) | |
| static if (hasElaborateDestructor!T) |
Don't limit this to structs. Classes can have destructors too.
| { | ||
| try | ||
| { | ||
| finalize_array!T(arr.ptr + reqsize, cursize - reqsize); |
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You can inline the function call here
| for (auto curP = p + size - tsize; curP >= p; curP -= tsize) | ||
| { | ||
| // call destructor | ||
| destroy(*cast(T*)curP); |
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| destroy(*cast(T*)curP); | |
| (cast(T*) curP).__xdtor(); |
This calls the destructor directly since you already know the type has one.
| // Shrinking a shared array | ||
| @safe unittest | ||
| { | ||
| shared(int)[] arr = new shared int[100]; | ||
| arr.length = 10; | ||
| _d_arrayshrinkfit!(shared int)(cast(void[])arr); | ||
| assert(arr.length == 10); | ||
| } | ||
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| // Shrink array with no elements (ptr is null) | ||
| @safe unittest | ||
| { | ||
| int[] arr; | ||
| assert(arr.ptr is null); | ||
| _d_arrayshrinkfit!int(arr); // should be a no-op | ||
| assert(arr.length == 0); | ||
| } | ||
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| // Shrinking an array of class references (destroyable via GC) | ||
| @safe unittest | ||
| { | ||
| class C { int x = 5; } | ||
| C[] arr = new C[10]; | ||
| foreach (ref c; arr) | ||
| c = new C(); | ||
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| arr.length = 3; | ||
| _d_arrayshrinkfit!C(arr); | ||
| assert(arr.length == 3); | ||
| foreach (c; arr) | ||
| assert(c !is null && c.x == 5); | ||
| } |
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The essence of _d_arrayshrinkfit is that any appends made after calling it will not reallocate. Testing if the elements are the same is fine, but the way to test this fully is to check if the array's .ptr is the same before and after calling the hook.
| bool gc_shrinkArrayUsed(void[] slice, size_t existingUsed, bool atomic) nothrow; | ||
| void[] gc_getArrayUsed(void *ptr, bool atomic) nothrow; |
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| bool gc_shrinkArrayUsed(void[] slice, size_t existingUsed, bool atomic) nothrow; | |
| void[] gc_getArrayUsed(void *ptr, bool atomic) nothrow; | |
| bool gc_shrinkArrayUsed(void[] slice, size_t existingUsed, bool atomic) pure nothrow; | |
| void[] gc_getArrayUsed(void *ptr, bool atomic) pure nothrow; |
You'll most likely have to lie about purity too.
Draft PR: Possible duplicate of #21152 This PR completely templatizes the _d_arrayshrinkfit hook and adds more unittests that cover good edge cases. This PR may be deleted if there is a conflict, and is therefore a draft.
This PR introduces a template version of the _d_arrayshrinkfit DRuntime Hook, often used as a call with
assumesafeappend.Changes Made