From 731c6d3fbbd935233513f4779e19b4ca18c2006e Mon Sep 17 00:00:00 2001
From: kcbanner <kcbanner@gmail.com>
Date: Sat, 26 Aug 2023 17:55:12 -0400
Subject: [PATCH 1/4] linux: export elf_aux_maybe so that libraries can call
 getauxval

---
 lib/std/os/linux.zig | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 443bf8edf9..a959e195ea 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -153,6 +153,10 @@ pub usingnamespace @import("linux/io_uring.zig");
 
 /// Set by startup code, used by `getauxval`.
 pub var elf_aux_maybe: ?[*]std.elf.Auxv = null;
+pub extern var _elf_aux_maybe: ?[*]std.elf.Auxv;
+comptime {
+    @export(elf_aux_maybe, .{ .name = "_elf_aux_maybe", .linkage = .Weak });
+}
 
 /// See `std.elf` for the constants.
 pub fn getauxval(index: usize) usize {

From fba81cd6062df8a49f1ec7559bdaf8d9081fcd43 Mon Sep 17 00:00:00 2001
From: kcbanner <kcbanner@gmail.com>
Date: Sun, 27 Aug 2023 11:12:31 -0400
Subject: [PATCH 2/4] linux: instead of export elf_aux_maybe, export getauxval
 itself

---
 lib/std/os/linux.zig | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index a959e195ea..6c96347ac5 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -153,13 +153,11 @@ pub usingnamespace @import("linux/io_uring.zig");
 
 /// Set by startup code, used by `getauxval`.
 pub var elf_aux_maybe: ?[*]std.elf.Auxv = null;
-pub extern var _elf_aux_maybe: ?[*]std.elf.Auxv;
-comptime {
-    @export(elf_aux_maybe, .{ .name = "_elf_aux_maybe", .linkage = .Weak });
-}
 
 /// See `std.elf` for the constants.
-pub fn getauxval(index: usize) usize {
+/// This matches the libc getauxval function.
+pub extern fn getauxval(index: usize) usize;
+fn getauxvalImpl(index: usize) callconv(.C) usize {
     const auxv = elf_aux_maybe orelse return 0;
     var i: usize = 0;
     while (auxv[i].a_type != std.elf.AT_NULL) : (i += 1) {
@@ -168,6 +166,9 @@ pub fn getauxval(index: usize) usize {
     }
     return 0;
 }
+comptime {
+    @export(getauxvalImpl, .{ .name = "getauxval", .linkage = .Weak });
+}
 
 // Some architectures (and some syscalls) require 64bit parameters to be passed
 // in a even-aligned register pair.

From fb0cef8522968af6a15fe953b8f259f3f0a7b37c Mon Sep 17 00:00:00 2001
From: kcbanner <kcbanner@gmail.com>
Date: Sun, 27 Aug 2023 16:52:43 -0400
Subject: [PATCH 3/4] linux: only export getauxval if not linking libc

---
 lib/std/os/linux.zig | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 6c96347ac5..c967c1dd7b 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -167,7 +167,9 @@ fn getauxvalImpl(index: usize) callconv(.C) usize {
     return 0;
 }
 comptime {
-    @export(getauxvalImpl, .{ .name = "getauxval", .linkage = .Weak });
+    if (!builtin.link_libc) {
+        @export(getauxvalImpl, .{ .name = "getauxval", .linkage = .Weak });
+    }
 }
 
 // Some architectures (and some syscalls) require 64bit parameters to be passed

From 2e2d6d2c3dcaccb101c97cf81e7a5f2afdf1ed49 Mon Sep 17 00:00:00 2001
From: kcbanner <kcbanner@gmail.com>
Date: Sun, 27 Aug 2023 19:50:57 -0400
Subject: [PATCH 4/4] linux: fixup for platforms that don't support extern
 functions yet

---
 lib/std/os/linux.zig | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index c967c1dd7b..9d3dcac559 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -154,9 +154,21 @@ pub usingnamespace @import("linux/io_uring.zig");
 /// Set by startup code, used by `getauxval`.
 pub var elf_aux_maybe: ?[*]std.elf.Auxv = null;
 
-/// See `std.elf` for the constants.
-/// This matches the libc getauxval function.
-pub extern fn getauxval(index: usize) usize;
+pub usingnamespace if (switch (builtin.zig_backend) {
+    // Calling extern functions is not yet supported with these backends
+    .stage2_x86_64, .stage2_aarch64, .stage2_arm, .stage2_riscv64, .stage2_sparc64 => false,
+    else => !builtin.link_libc,
+}) struct {
+    /// See `std.elf` for the constants.
+    /// This matches the libc getauxval function.
+    pub extern fn getauxval(index: usize) usize;
+    comptime {
+        @export(getauxvalImpl, .{ .name = "getauxval", .linkage = .Weak });
+    }
+} else struct {
+    pub const getauxval = getauxvalImpl;
+};
+
 fn getauxvalImpl(index: usize) callconv(.C) usize {
     const auxv = elf_aux_maybe orelse return 0;
     var i: usize = 0;
@@ -166,11 +178,6 @@ fn getauxvalImpl(index: usize) callconv(.C) usize {
     }
     return 0;
 }
-comptime {
-    if (!builtin.link_libc) {
-        @export(getauxvalImpl, .{ .name = "getauxval", .linkage = .Weak });
-    }
-}
 
 // Some architectures (and some syscalls) require 64bit parameters to be passed
 // in a even-aligned register pair.