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std: remove meta.assumeSentinel

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All but 3 callsites of this function in the standard library and
compiler were unnecessary and were removed in faf2fd18.

In this commit, the remaining 3 callsites are removed. One of them
turned out to also be unnecessary and has been replaced by slicing
directly with the length..

The 2 remaining callsites were in the very pointer-math heavy
std/os/linux/vdso.zig code which should perhaps be refactored to better
utilize slices. These 2 callsites are replaced with a plain
@ptrCast([*:0]u8, ptr) though could likely use std.mem.sliceTo() if the
surrounding code was refactored.
This commit is contained in:
Isaac Freund 2023-01-24 11:37:30 +01:00 committed by Andrew Kelley
parent 4e80253e20
commit 9eeae556cc
3 changed files with 4 additions and 38 deletions
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2
lib/std/fs.zig
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@ -3028,7 +3028,7 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
/// The result is UTF16LE-encoded.
pub fn selfExePathW() [:0]const u16 {
const image_path_name = &os.windows.peb().ProcessParameters.ImagePathName;
return mem.sliceTo(std.meta.assumeSentinel(image_path_name.Buffer, 0), 0);
return image_path_name.Buffer[0 .. image_path_name.Length / 2 :0];
}
/// `selfExeDirPath` except allocates the result on the heap.

36
lib/std/meta.zig
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@ -332,41 +332,7 @@ pub fn Sentinel(comptime T: type, comptime sentinel_val: Elem(T)) type {
@compileError("Unable to derive a sentinel pointer type from " ++ @typeName(T));
}
/// Takes a Slice or Many Pointer and returns it with the Type modified to have the given sentinel value.
/// This function assumes the caller has verified the memory contains the sentinel value.
pub fn assumeSentinel(p: anytype, comptime sentinel_val: Elem(@TypeOf(p))) Sentinel(@TypeOf(p), sentinel_val) {
const T = @TypeOf(p);
const ReturnType = Sentinel(T, sentinel_val);
switch (@typeInfo(T)) {
.Pointer => |info| switch (info.size) {
.Slice, .Many, .One => return @ptrCast(ReturnType, p),
.C => {},
},
.Optional => |info| switch (@typeInfo(info.child)) {
.Pointer => |ptr_info| switch (ptr_info.size) {
.Many => return @ptrCast(ReturnType, p),
else => {},
},
else => {},
},
else => {},
}
@compileError("Unable to derive a sentinel pointer type from " ++ @typeName(T));
}
test "std.meta.assumeSentinel" {
try testing.expect([*:0]u8 == @TypeOf(assumeSentinel(@as([*]u8, undefined), 0)));
try testing.expect([:0]u8 == @TypeOf(assumeSentinel(@as([]u8, undefined), 0)));
try testing.expect([*:0]const u8 == @TypeOf(assumeSentinel(@as([*]const u8, undefined), 0)));
try testing.expect([:0]const u8 == @TypeOf(assumeSentinel(@as([]const u8, undefined), 0)));
try testing.expect([*:0]u16 == @TypeOf(assumeSentinel(@as([*]u16, undefined), 0)));
try testing.expect([:0]const u16 == @TypeOf(assumeSentinel(@as([]const u16, undefined), 0)));
try testing.expect([*:3]u8 == @TypeOf(assumeSentinel(@as([*:1]u8, undefined), 3)));
try testing.expect([:null]?[*]u8 == @TypeOf(assumeSentinel(@as([]?[*]u8, undefined), null)));
try testing.expect([*:null]?[*]u8 == @TypeOf(assumeSentinel(@as([*]?[*]u8, undefined), null)));
try testing.expect(*[10:0]u8 == @TypeOf(assumeSentinel(@as(*[10]u8, undefined), 0)));
try testing.expect(?[*:0]u8 == @TypeOf(assumeSentinel(@as(?[*]u8, undefined), 0)));
}
const assumeSentinel = @compileError("This function has been removed, consider using std.mem.sliceTo() or if needed a @ptrCast()");
pub fn containerLayout(comptime T: type) Type.ContainerLayout {
return switch (@typeInfo(T)) {

4
lib/std/os/linux/vdso.zig
View File

@ -68,7 +68,7 @@ pub fn lookup(vername: []const u8, name: []const u8) usize {
if (0 == (@as(u32, 1) << @intCast(u5, syms[i].st_info & 0xf) & OK_TYPES)) continue;
if (0 == (@as(u32, 1) << @intCast(u5, syms[i].st_info >> 4) & OK_BINDS)) continue;
if (0 == syms[i].st_shndx) continue;
const sym_name = std.meta.assumeSentinel(strings + syms[i].st_name, 0);
const sym_name = @ptrCast([*:0]u8, strings + syms[i].st_name);
if (!mem.eql(u8, name, mem.sliceTo(sym_name, 0))) continue;
if (maybe_versym) |versym| {
if (!checkver(maybe_verdef.?, versym[i], vername, strings))
@ -91,6 +91,6 @@ fn checkver(def_arg: *elf.Verdef, vsym_arg: i32, vername: []const u8, strings: [
def = @intToPtr(*elf.Verdef, @ptrToInt(def) + def.vd_next);
}
const aux = @intToPtr(*elf.Verdaux, @ptrToInt(def) + def.vd_aux);
const vda_name = std.meta.assumeSentinel(strings + aux.vda_name, 0);
const vda_name = @ptrCast([*:0]u8, strings + aux.vda_name);
return mem.eql(u8, vername, mem.sliceTo(vda_name, 0));
}