Add assert.h, fix installation of headers

build.zig

@@ -14,6 +14,11 @@ pub fn createLibrary(b: *std.Build, target: std.zig.CrossTarget, optimize: std.b
     });
 
     libc.addIncludePath(.{ .path = "include" });
+    for (header_files) |header_name|
+        libc.installHeader(
+            b.fmt("include/{s}", .{header_name}),
+            header_name,
+        );
 
     return libc;
 }
@@ -39,13 +44,6 @@ pub fn build(b: *std.Build) void {
     libc.single_threaded = single_threaded;
     b.installArtifact(libc);
 
-    for (header_files) |header_name| {
-        b.getInstallStep().dependOn(&b.addInstallHeaderFile(
-            b.fmt("include/{s}", .{header_name}),
-            header_name,
-        ).step);
-    }
-
     // test suite:
     {
         // Compile for huge amount of targets to detect breakage early on:
@@ -118,6 +116,7 @@ pub fn build(b: *std.Build) void {
 }
 
 const header_files = [_][]const u8{
+    "assert.h",
     "ctype.h",
     "errno.h",
     "inttypes.h",

include/assert.h

@@ -0,0 +1,16 @@
+#ifndef _FOUNDATION_LIBC_ASSERT_H_
+#define _FOUNDATION_LIBC_ASSERT_H_
+
+#ifndef NDEBUG
+#define assert(expr)
+#else
+extern void __assert(char const * assertion, char const * file, unsigned line) __attribute__((__noreturn__));
+
+#define assert(expr) \
+    ((expr)          \
+         ? void(0)   \
+         : __assert(#expr, __FILE__, __LINE__))
+
+#endif
+
+#endif

src/libc.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const builtin = @import("builtin");
 
 pub const h = @cImport({
+    @cInclude("assert.h");
     @cInclude("ctype.h");
     @cInclude("errno.h");
     @cInclude("inttypes.h");
@@ -11,6 +12,7 @@ pub const h = @cImport({
     @cInclude("string.h");
     @cInclude("tgmath.h");
     @cInclude("uchar.h");
+
     @cInclude("foundation/libc.h");
 });
 
@@ -33,6 +35,7 @@ comptime {
 
 comptime {
     // Drag in all implementations, so they are compiled:
+    _ = @import("modules/assert.zig");
     _ = @import("modules/ctype.zig");
     _ = @import("modules/errno.zig");
     _ = @import("modules/math.zig");

src/modules/assert.zig

@@ -0,0 +1,14 @@
+const std = @import("std");
+
+export fn __assert(
+    assertion: ?[*:0]const u8,
+    file: ?[*:0]const u8,
+    line: c_uint,
+) noreturn {
+    var buf: [256]u8 = undefined;
+    const str = std.fmt.bufPrint(&buf, "assertion failed: '{?s}' in file {?s} line {}", .{ assertion, file, line }) catch {
+        @panic("assertion failed");
+    };
+
+    @panic(str);
+}