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std › heap › testAllocatorLargeAlignment

testAllocatorLargeAlignment

Function parameters

Parameters

#
base_allocator:mem.Allocator

Type definitions in this namespace

Types

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GeneralPurposeAllocatorConfig
Deprecated; to be removed after 0.14.0 is tagged.

Functions in this namespace

Functions

#
GeneralPurposeAllocator
Deprecated; to be removed after 0.14.0 is tagged.
pageSize
If the page size is comptime-known, return value is comptime.
defaultQueryPageSize
The default implementation of `std.options.queryPageSize`.
stackFallback
Returns a `StackFallbackAllocator` allocating using either a
StackFallbackAllocator
An allocator that attempts to allocate using a
testAllocator
This one should not try alignments that exceed what C malloc can handle.

TODO Utilize this on Windows.

Values

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next_mmap_addr_hint
TODO Utilize this on Windows.
page_size_min
comptime-known minimum page size of the target.
page_size_max
comptime-known maximum page size of the target.
c_allocator
Supports the full Allocator interface, including alignment, and exploiting
raw_c_allocator
Asserts allocations are within `@alignOf(std.c.max_align_t)` and directly
page_allocator
On operating systems that support memory mapping, this allocator makes a
smp_allocator
= .{ .ptr = undefined, .vtable = &SmpAllocator.vtable, }
wasm_allocator
This allocator is fast, small, and specific to WebAssembly.

Source

Implementation

#
pub fn testAllocatorLargeAlignment(base_allocator: mem.Allocator) !void {
    var validationAllocator = mem.validationWrap(base_allocator);
    const allocator = validationAllocator.allocator();

    const large_align: usize = page_size_min / 2;

    var align_mask: usize = undefined;
    align_mask = @shlWithOverflow(~@as(usize, 0), @as(Allocator.Log2Align, @ctz(large_align)))[0];

    var slice = try allocator.alignedAlloc(u8, .fromByteUnits(large_align), 500);
    try testing.expect(@intFromPtr(slice.ptr) & align_mask == @intFromPtr(slice.ptr));

    if (allocator.resize(slice, 100)) {
        slice = slice[0..100];
    }

    slice = try allocator.realloc(slice, 5000);
    try testing.expect(@intFromPtr(slice.ptr) & align_mask == @intFromPtr(slice.ptr));

    if (allocator.resize(slice, 10)) {
        slice = slice[0..10];
    }

    slice = try allocator.realloc(slice, 20000);
    try testing.expect(@intFromPtr(slice.ptr) & align_mask == @intFromPtr(slice.ptr));

    allocator.free(slice);
}