From b1eb831aba6eec78f367053200007c867817e811 Mon Sep 17 00:00:00 2001
From: daurnimator <quae@daurnimator.com>
Date: Wed, 1 Apr 2020 01:44:14 +1100
Subject: [PATCH 1/2] std: fix mem.span* when an optional pointer is passed

---
 lib/std/mem.zig | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/lib/std/mem.zig b/lib/std/mem.zig
index d4d0a83f4..f54eb03d6 100644
--- a/lib/std/mem.zig
+++ b/lib/std/mem.zig
@@ -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];
@@ -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];
@@ -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,

From 3cf302a71d50114c44cedbe0114e513063b93302 Mon Sep 17 00:00:00 2001
From: daurnimator <quae@daurnimator.com>
Date: Wed, 1 Apr 2020 01:25:25 +1100
Subject: [PATCH 2/2] Tidy up some mem.spanZ use-sites now that null is
 accepted

---
 lib/std/debug.zig          | 2 +-
 lib/std/os.zig             | 2 +-
 src-self-hosted/stage2.zig | 7 +++----
 3 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index 35c13809f..11d808a17 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -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;
diff --git a/lib/std/os.zig b/lib/std/os.zig
index e9e3b449f..48d82797b 100644
--- a/lib/std/os.zig
+++ b/lib/std/os.zig
@@ -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);
diff --git a/src-self-hosted/stage2.zig b/src-self-hosted/stage2.zig
index fcf963409..d9b763912 100644
--- a/src-self-hosted/stage2.zig
+++ b/src-self-hosted/stage2.zig
@@ -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);
+    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,