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Take advantage of mem.spanZ accepting null #4880

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Merged
merged 2 commits into from
Mar 31, 2020
Merged

Take advantage of mem.spanZ accepting null #4880

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b1eb831
std: fix mem.span* when an optional pointer is passed
daurnimator Mar 31, 2020
3cf302a
Tidy up some mem.spanZ use-sites now that null is accepted
daurnimator Mar 31, 2020
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2 changes: 1 addition & 1 deletion lib/std/debug.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1254,7 +1254,7 @@ pub const DebugInfo = struct {
if (context.address >= seg_start and context.address < seg_end) {
// Android libc uses NULL instead of an empty string to mark the
// main program
context.name = if (info.dlpi_name) |dlpi_name| mem.spanZ(dlpi_name) else "";
context.name = mem.spanZ(info.dlpi_name) orelse "";
context.base_address = info.dlpi_addr;
// Stop the iteration
return error.Found;
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22 changes: 16 additions & 6 deletions lib/std/mem.zig
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Expand Up @@ -559,10 +559,14 @@ test "Span" {
/// When there is both a sentinel and an array length or slice length, the
/// length value is used instead of the sentinel.
pub fn span(ptr: var) Span(@TypeOf(ptr)) {
const Result = Span(@TypeOf(ptr));
if (@typeInfo(@TypeOf(ptr)) == .Optional and ptr == null) {
return null;
if (@typeInfo(@TypeOf(ptr)) == .Optional) {
if (ptr) |non_null| {
return span(non_null);
} else {
return null;
}
}
const Result = Span(@TypeOf(ptr));
const l = len(ptr);
if (@typeInfo(Result).Pointer.sentinel) |s| {
return ptr[0..l :s];
Expand All @@ -576,16 +580,21 @@ test "span" {
const ptr = @as([*:3]u16, array[0..2 :3]);
testing.expect(eql(u16, span(ptr), &[_]u16{ 1, 2 }));
testing.expect(eql(u16, span(&array), &[_]u16{ 1, 2, 3, 4, 5 }));
testing.expectEqual(@as(?[:0]u16, null), span(@as(?[*:0]u16, null)));
}

/// Same as `span`, except when there is both a sentinel and an array
/// length or slice length, scans the memory for the sentinel value
/// rather than using the length.
pub fn spanZ(ptr: var) Span(@TypeOf(ptr)) {
const Result = Span(@TypeOf(ptr));
if (@typeInfo(@TypeOf(ptr)) == .Optional and ptr == null) {
return null;
if (@typeInfo(@TypeOf(ptr)) == .Optional) {
if (ptr) |non_null| {
return spanZ(non_null);
} else {
return null;
}
}
const Result = Span(@TypeOf(ptr));
const l = lenZ(ptr);
if (@typeInfo(Result).Pointer.sentinel) |s| {
return ptr[0..l :s];
Expand All @@ -599,6 +608,7 @@ test "spanZ" {
const ptr = @as([*:3]u16, array[0..2 :3]);
testing.expect(eql(u16, spanZ(ptr), &[_]u16{ 1, 2 }));
testing.expect(eql(u16, spanZ(&array), &[_]u16{ 1, 2, 3, 4, 5 }));
testing.expectEqual(@as(?[:0]u16, null), spanZ(@as(?[*:0]u16, null)));
}

/// Takes a pointer to an array, an array, a sentinel-terminated pointer,
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2 changes: 1 addition & 1 deletion lib/std/os.zig
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Expand Up @@ -1078,7 +1078,7 @@ pub fn execvpe_expandArg0(
mem.set(?[*:0]u8, argv_buf, null);
defer {
for (argv_buf) |arg| {
const arg_buf = if (arg) |ptr| mem.spanZ(ptr) else break;
const arg_buf = mem.spanZ(arg) orelse break;
allocator.free(arg_buf);
}
allocator.free(argv_buf);
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7 changes: 3 additions & 4 deletions src-self-hosted/stage2.zig
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Expand Up @@ -689,12 +689,11 @@ fn stage2CrossTarget(
mcpu_oz: ?[*:0]const u8,
dynamic_linker_oz: ?[*:0]const u8,
) !CrossTarget {
const zig_triple = if (zig_triple_oz) |zig_triple_z| mem.spanZ(zig_triple_z) else "native";
const mcpu = if (mcpu_oz) |mcpu_z| mem.spanZ(mcpu_z) else null;
const dynamic_linker = if (dynamic_linker_oz) |dl_z| mem.spanZ(dl_z) else null;
const mcpu = mem.spanZ(mcpu_oz);
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Fun bug: if I inlined this into the following expression I got:

broken LLVM module found: Call parameter type does not match function signature!
  %67 = getelementptr inbounds %std.zig.cross_target.ParseOptions, %std.zig.cross_target.ParseOptions* %10, i32 0, i32 1, !dbg !20878
 %"?[:0]const u8"*  call fastcc void @std.mem.spanZ.176(%"?[]const u8"* sret %67, i8* %68), !dbg !20880

This is a bug in the Zig compiler.

const dynamic_linker = mem.spanZ(dynamic_linker_oz);
var diags: CrossTarget.ParseOptions.Diagnostics = .{};
const target: CrossTarget = CrossTarget.parse(.{
.arch_os_abi = zig_triple,
.arch_os_abi = mem.spanZ(zig_triple_oz) orelse "native",
.cpu_features = mcpu,
.dynamic_linker = dynamic_linker,
.diagnostics = &diags,
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