From 259b7c3f3fc3f8902f8aa4e6e7539df271073a47 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 30 Jul 2025 18:58:47 +0200
Subject: [PATCH 1/2] std.Target: pull Os.requiresLibC() up to Target

---
 lib/std/Target.zig | 101 ++++++++++++++++++++++-----------------------
 src/target.zig     |   2 +-
 2 files changed, 51 insertions(+), 52 deletions(-)

diff --git a/lib/std/Target.zig b/lib/std/Target.zig
index c75e2b51fb..ccc8ab79d8 100644
--- a/lib/std/Target.zig
+++ b/lib/std/Target.zig
@@ -697,57 +697,6 @@ pub const Os = struct {
             => |field| @field(os.version_range, @tagName(field)).isAtLeast(ver),
         };
     }
-
-    /// On Darwin, we always link libSystem which contains libc.
-    /// Similarly on FreeBSD and NetBSD we always link system libc
-    /// since this is the stable syscall interface.
-    pub fn requiresLibC(os: Os) bool {
-        return switch (os.tag) {
-            .aix,
-            .driverkit,
-            .macos,
-            .ios,
-            .tvos,
-            .watchos,
-            .visionos,
-            .dragonfly,
-            .openbsd,
-            .haiku,
-            .solaris,
-            .illumos,
-            .serenity,
-            => true,
-
-            .linux,
-            .windows,
-            .freebsd,
-            .netbsd,
-            .freestanding,
-            .fuchsia,
-            .ps3,
-            .zos,
-            .rtems,
-            .cuda,
-            .nvcl,
-            .amdhsa,
-            .ps4,
-            .ps5,
-            .mesa3d,
-            .contiki,
-            .amdpal,
-            .hermit,
-            .hurd,
-            .wasi,
-            .emscripten,
-            .uefi,
-            .opencl,
-            .opengl,
-            .vulkan,
-            .plan9,
-            .other,
-            => false,
-        };
-    }
 };
 
 pub const aarch64 = @import("Target/aarch64.zig");
@@ -2055,6 +2004,56 @@ pub inline fn isWasiLibC(target: *const Target) bool {
     return target.os.tag == .wasi and target.abi.isMusl();
 }
 
+/// Does this target require linking libc? This may be the case if the target has an unstable
+/// syscall interface, for example.
+pub fn requiresLibC(target: *const Target) bool {
+    return switch (target.os.tag) {
+        .aix,
+        .driverkit,
+        .macos,
+        .ios,
+        .tvos,
+        .watchos,
+        .visionos,
+        .dragonfly,
+        .openbsd,
+        .haiku,
+        .solaris,
+        .illumos,
+        .serenity,
+        => true,
+
+        .linux
+        .windows,
+        .freebsd,
+        .netbsd,
+        .freestanding,
+        .fuchsia,
+        .ps3,
+        .zos,
+        .rtems,
+        .cuda,
+        .nvcl,
+        .amdhsa,
+        .ps4,
+        .ps5,
+        .mesa3d,
+        .contiki,
+        .amdpal,
+        .hermit,
+        .hurd,
+        .wasi,
+        .emscripten,
+        .uefi,
+        .opencl,
+        .opengl,
+        .vulkan,
+        .plan9,
+        .other,
+        => false,
+    };
+}
+
 pub const DynamicLinker = struct {
     /// Contains the memory used to store the dynamic linker path. This field
     /// should not be used directly. See `get` and `set`. This field exists so
diff --git a/src/target.zig b/src/target.zig
index ad83414c23..dbcfe341a4 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -20,7 +20,7 @@ pub fn cannotDynamicLink(target: *const std.Target) bool {
 /// Similarly on FreeBSD and NetBSD we always link system libc
 /// since this is the stable syscall interface.
 pub fn osRequiresLibC(target: *const std.Target) bool {
-    return target.os.requiresLibC();
+    return target.requiresLibC();
 }
 
 pub fn libCNeedsLibUnwind(target: *const std.Target, link_mode: std.builtin.LinkMode) bool {

From 03facba4963abd142985c9617ca38de46b1615f1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 30 Jul 2025 18:59:08 +0200
Subject: [PATCH 2/2] std.Target: require libc for Android API levels prior to
 29

Emulated TLS depends on libc pthread functions.

Closes #24589.
---
 lib/std/Target.zig | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/std/Target.zig b/lib/std/Target.zig
index ccc8ab79d8..fb9149c759 100644
--- a/lib/std/Target.zig
+++ b/lib/std/Target.zig
@@ -2023,7 +2023,12 @@ pub fn requiresLibC(target: *const Target) bool {
         .serenity,
         => true,
 
-        .linux
+        // Android API levels prior to 29 did not have native TLS support. For these API levels, TLS
+        // is implemented through calls to `__emutls_get_address`. We provide this function in
+        // compiler-rt, but it's implemented by way of `pthread_key_create` et al, so linking libc
+        // is required.
+        .linux => target.abi.isAndroid() and target.os.version_range.linux.android < 29,
+
         .windows,
         .freebsd,
         .netbsd,