libc: strdup, strndup, wcsdup (#31935)

Contributes to: #30978

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31935
Reviewed-by: Andrew Kelley <andrew@ziglang.org>

lib/c/string.zig

@@ -1,6 +1,7 @@
 const builtin = @import("builtin");
 const std = @import("std");
 const symbol = @import("../c.zig").symbol;
+const c = std.c;
 
 comptime {
     if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
@@ -24,6 +25,8 @@ comptime {
         symbol(&strpbrk, "strpbrk");
         symbol(&strstr, "strstr");
         symbol(&strtok, "strtok");
+        symbol(&strdup, "strdup");
+        symbol(&strndup, "strndup");
         // strlen is in compiler_rt
 
         symbol(&strtok_r, "strtok_r");
@@ -164,6 +167,23 @@ fn strtok(noalias maybe_str: ?[*:0]c_char, noalias values: [*:0]const c_char) ca
     return strtok_r(maybe_str, values, &state.str);
 }
 
+fn strdup(str: [*:0]const c_char) callconv(.c) ?[*:0]c_char {
+    const len = std.mem.len(str);
+    const d_opaque = c.malloc(len + 1) orelse return null;
+    const d: [*]c_char = @ptrCast(d_opaque);
+    @memcpy(d[0 .. len + 1], str[0 .. len + 1]);
+    return @ptrCast(d);
+}
+
+fn strndup(str: [*:0]const c_char, n: usize) callconv(.c) ?[*:0]c_char {
+    const len = strnlen(str, n);
+    const d_opaque = c.malloc(len + 1) orelse return null;
+    const d: [*]c_char = @ptrCast(d_opaque);
+    @memcpy(d[0..len], str[0..len]);
+    d[len] = 0;
+    return @ptrCast(d);
+}
+
 // strlen is in compiler_rt
 
 fn strtok_r(noalias maybe_str: ?[*:0]c_char, noalias values: [*:0]const c_char, noalias state: *?[*:0]c_char) callconv(.c) ?[*:0]c_char {

lib/c/wchar.zig

@@ -5,6 +5,7 @@ const wint_t = std.c.wint_t;
 const wchar_t = std.c.wchar_t;
 
 const symbol = @import("../c.zig").symbol;
+const c = std.c;
 
 comptime {
     if (builtin.target.isMuslLibC() or builtin.target.isWasiLibC()) {
@@ -30,6 +31,7 @@ comptime {
         symbol(&wcspbrk, "wcspbrk");
         symbol(&wcstok, "wcstok");
         symbol(&wcsstr, "wcsstr");
+        symbol(&wcsdup, "wcsdup");
         symbol(&wcswcs, "wcswcs");
     }
 
@@ -189,3 +191,11 @@ fn wcsstr(noalias haystack: [*:0]const wchar_t, noalias needle: [*:0]const wchar
 fn wcswcs(noalias haystack: [*:0]const wchar_t, noalias needle: [*:0]const wchar_t) callconv(.c) ?[*:0]wchar_t {
     return wcsstr(haystack, needle);
 }
+
+fn wcsdup(str: [*:0]const wchar_t) callconv(.c) ?[*:0]wchar_t {
+    const len = wcslen(str);
+    const size = (len + 1) * @sizeOf(wchar_t);
+    const d_opaque = c.malloc(size) orelse return null;
+    const d: [*]wchar_t = @ptrCast(@alignCast(d_opaque));
+    return @ptrCast(wmemcpy(d, str, len + 1));
+}

lib/libc/musl/src/string/strdup.c

@@ -1,10 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-
-char *strdup(const char *s)
-{
-	size_t l = strlen(s);
-	char *d = malloc(l+1);
-	if (!d) return NULL;
-	return memcpy(d, s, l+1);
-}

lib/libc/musl/src/string/strndup.c

@@ -1,12 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-
-char *strndup(const char *s, size_t n)
-{
-	size_t l = strnlen(s, n);
-	char *d = malloc(l+1);
-	if (!d) return NULL;
-	memcpy(d, s, l);
-	d[l] = 0;
-	return d;
-}

lib/libc/musl/src/string/wcsdup.c

@@ -1,10 +0,0 @@
-#include <stdlib.h>
-#include <wchar.h>
-
-wchar_t *wcsdup(const wchar_t *s)
-{
-	size_t l = wcslen(s);
-	wchar_t *d = malloc((l+1)*sizeof(wchar_t));
-	if (!d) return NULL;
-	return wmemcpy(d, s, l+1);
-}

lib/std/c.zig

@@ -11136,6 +11136,9 @@ pub extern "c" fn swab(noalias from: *const anyopaque, noalias to: *anyopaque, n
 pub extern "c" fn strncmp(a: [*:0]const c_char, b: [*:0]const c_char, max: usize) c_int;
 pub extern "c" fn strcasecmp(a: [*:0]const c_char, b: [*:0]const c_char) c_int;
 pub extern "c" fn strncasecmp(a: [*:0]const c_char, b: [*:0]const c_char, max: usize) c_int;
+pub extern "c" fn strdup(s: [*:0]const c_char) ?[*:0]c_char;
+pub extern "c" fn strndup(s: [*:0]const c_char, n: usize) ?[*:0]c_char;
+pub extern "c" fn wcsdup(s: [*:0]const wchar_t) ?[*:0]wchar_t;
 
 pub extern "c" fn ffs(i: c_int) c_int;
 pub extern "c" fn ffsl(i: c_long) c_long;