From ad3828db45b7830d5953e7c728c227e78f574cf9 Mon Sep 17 00:00:00 2001
From: GasInfinity <me@gasinfinity.dev>
Date: Tue, 13 Jan 2026 22:14:07 +0100
Subject: [PATCH] feat(libzigc): use common `rand` implementations

* also remove their musl implementation
---
 lib/c/stdlib.zig                |  2 ++
 lib/c/stdlib/rand.zig           | 30 ++++++++++++++++++++++++++++++
 lib/libc/musl/src/prng/rand.c   | 15 ---------------
 lib/libc/musl/src/prng/rand_r.c | 15 ---------------
 src/libs/musl.zig               |  2 --
 src/libs/wasi_libc.zig          |  2 --
 6 files changed, 32 insertions(+), 34 deletions(-)
 create mode 100644 lib/c/stdlib/rand.zig
 delete mode 100644 lib/libc/musl/src/prng/rand.c
 delete mode 100644 lib/libc/musl/src/prng/rand_r.c

diff --git a/lib/c/stdlib.zig b/lib/c/stdlib.zig
index 67b6345b13fd3217670031586ce009b40e6950a6..6ee0d19fb524f44f16bca6ef2939b93aba42a819 100644
--- a/lib/c/stdlib.zig
+++ b/lib/c/stdlib.zig
@@ -7,6 +7,8 @@ const ldiv_t = std.c.ldiv_t;
 const lldiv_t = std.c.lldiv_t;
 
 comptime {
+    _ = @import("stdlib/rand.zig");
+
     if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
         // Functions specific to musl and wasi-libc.
         @export(&abs, .{ .name = "abs", .linkage = common.linkage, .visibility = common.visibility });
diff --git a/lib/c/stdlib/rand.zig b/lib/c/stdlib/rand.zig
new file mode 100644
index 0000000000000000000000000000000000000000..9ca7a51967a40fa8d180ae4aff8eaf763cdd3bb2
--- /dev/null
+++ b/lib/c/stdlib/rand.zig
@@ -0,0 +1,30 @@
+const std = @import("std");
+const common = @import("../common.zig");
+const builtin = @import("builtin");
+
+comptime {
+    if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
+        @export(&rand, .{ .name = "rand", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&srand, .{ .name = "srand", .linkage = common.linkage, .visibility = common.visibility });
+        @export(&rand_r, .{ .name = "rand_r", .linkage = common.linkage, .visibility = common.visibility });
+    }
+}
+
+// NOTE: The PRNG used for `rand` is unspecified, so it can be any!
+var rand_state: std.Random.SplitMix64 = .init(1);
+
+fn rand_r(seed: *c_uint) callconv(.c) c_int {
+    var mix: std.Random.SplitMix64 = .init(seed.*);
+    defer seed.* = @truncate(mix.s);
+
+    // Every bundled libc defines RAND_MAX as `std.math.maxInt(u31)` (except windows where it is `std.math.maxInt(u15)`)
+    return @as(u31, @truncate(mix.next() >> 33));
+}
+
+fn srand(seed: c_uint) callconv(.c) void {
+    rand_state = .init(seed);
+}
+
+fn rand() callconv(.c) c_int {
+    return @as(u31, @truncate(rand_state.next() >> 33));
+}
diff --git a/lib/libc/musl/src/prng/rand.c b/lib/libc/musl/src/prng/rand.c
deleted file mode 100644
index c000cd248cef667bab257940768616c9349f7d70..0000000000000000000000000000000000000000
--- a/lib/libc/musl/src/prng/rand.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <stdlib.h>
-#include <stdint.h>
-
-static uint64_t seed;
-
-void srand(unsigned s)
-{
-	seed = s-1;
-}
-
-int rand(void)
-{
-	seed = 6364136223846793005ULL*seed + 1;
-	return seed>>33;
-}
diff --git a/lib/libc/musl/src/prng/rand_r.c b/lib/libc/musl/src/prng/rand_r.c
deleted file mode 100644
index 638614c867911a133d4a3f054c7150e28d5a4425..0000000000000000000000000000000000000000
--- a/lib/libc/musl/src/prng/rand_r.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <stdlib.h>
-
-static unsigned temper(unsigned x)
-{
-	x ^= x>>11;
-	x ^= x<<7 & 0x9D2C5680;
-	x ^= x<<15 & 0xEFC60000;
-	x ^= x>>18;
-	return x;
-}
-
-int rand_r(unsigned *seed)
-{
-	return temper(*seed = *seed * 1103515245 + 12345)/2;
-}
diff --git a/src/libs/musl.zig b/src/libs/musl.zig
index e2d683ae69d81119a9be641180dc96301feb8190..e7cea46f0ccf7c155f9a8bb4a3b001a0375d62c4 100644
--- a/src/libs/musl.zig
+++ b/src/libs/musl.zig
@@ -1310,9 +1310,7 @@ const src_files = [_][]const u8{
     "musl/src/prng/lrand48.c",
     "musl/src/prng/mrand48.c",
     "musl/src/prng/__rand48_step.c",
-    "musl/src/prng/rand.c",
     "musl/src/prng/random.c",
-    "musl/src/prng/rand_r.c",
     "musl/src/prng/__seed48.c",
     "musl/src/prng/seed48.c",
     "musl/src/prng/srand48.c",
diff --git a/src/libs/wasi_libc.zig b/src/libs/wasi_libc.zig
index 3b4fa178d1ad3f59aa9c559f88f15faadc86dd72..afee02912170a483c33446221d2a6ecc3507f025 100644
--- a/src/libs/wasi_libc.zig
+++ b/src/libs/wasi_libc.zig
@@ -890,8 +890,6 @@ const libc_top_half_src_files = [_][]const u8{
     "musl/src/prng/lrand48.c",
     "musl/src/prng/mrand48.c",
     "musl/src/prng/__rand48_step.c",
-    "musl/src/prng/rand.c",
-    "musl/src/prng/rand_r.c",
     "musl/src/prng/__seed48.c",
     "musl/src/prng/seed48.c",
     "musl/src/prng/srand48.c",
-- 
2.54.0