native libc detection: respect spaces in CC env var

Zig has detection for when it is accidentally being called recursively
when trying to find the native libc installation. However it was not
working, resulting in a cryptic failure, because zig tried to execute
a command which had spaces in it rather than tokenizing it.

This improves the user experience of `zig cc` for systems that Zig
does not support cross-compiling for.

Closes #8960

Author: andrewrk

src/libc_installation.zig

@@ -237,26 +237,38 @@ pub const LibCInstallation = struct {
 
     fn findNativeIncludeDirPosix(self: *LibCInstallation, args: FindNativeOptions) FindError!void {
         const allocator = args.allocator;
+
+        // Detect infinite loops.
+        var env_map = try std.process.getEnvMap(allocator);
+        defer env_map.deinit();
+        const skip_cc_env_var = if (env_map.get(inf_loop_env_key)) |phase| blk: {
+            if (std.mem.eql(u8, phase, "1")) {
+                try env_map.put(inf_loop_env_key, "2");
+                break :blk true;
+            } else {
+                return error.ZigIsTheCCompiler;
+            }
+        } else blk: {
+            try env_map.put(inf_loop_env_key, "1");
+            break :blk false;
+        };
+
         const dev_null = if (is_windows) "nul" else "/dev/null";
-        const cc_exe = std.os.getenvZ("CC") orelse default_cc_exe;
-        const argv = [_][]const u8{
-            cc_exe,
+
+        var argv = std.ArrayList([]const u8).init(allocator);
+        defer argv.deinit();
+
+        try appendCcExe(&argv, skip_cc_env_var);
+        try argv.appendSlice(&.{
             "-E",
             "-Wp,-v",
             "-xc",
             dev_null,
-        };
-        var env_map = try std.process.getEnvMap(allocator);
-        defer env_map.deinit();
-
-        // Detect infinite loops.
-        const inf_loop_env_key = "ZIG_IS_DETECTING_LIBC_PATHS";
-        if (env_map.get(inf_loop_env_key) != null) return error.ZigIsTheCCompiler;
-        try env_map.put(inf_loop_env_key, "1");
+        });
 
         const exec_res = std.ChildProcess.exec(.{
             .allocator = allocator,
-            .argv = &argv,
+            .argv = argv.items,
             .max_output_bytes = 1024 * 1024,
             .env_map = &env_map,
             // Some C compilers, such as Clang, are known to rely on argv[0] to find the path
@@ -267,7 +279,7 @@ pub const LibCInstallation = struct {
         }) catch |err| switch (err) {
             error.OutOfMemory => return error.OutOfMemory,
             else => {
-                printVerboseInvocation(&argv, null, args.verbose, null);
+                printVerboseInvocation(argv.items, null, args.verbose, null);
                 return error.UnableToSpawnCCompiler;
             },
         };
@@ -277,11 +289,11 @@ pub const LibCInstallation = struct {
         }
         switch (exec_res.term) {
             .Exited => |code| if (code != 0) {
-                printVerboseInvocation(&argv, null, args.verbose, exec_res.stderr);
+                printVerboseInvocation(argv.items, null, args.verbose, exec_res.stderr);
                 return error.CCompilerExitCode;
             },
             else => {
-                printVerboseInvocation(&argv, null, args.verbose, exec_res.stderr);
+                printVerboseInvocation(argv.items, null, args.verbose, exec_res.stderr);
                 return error.CCompilerCrashed;
             },
         }
@@ -540,8 +552,6 @@ pub const LibCInstallation = struct {
     }
 };
 
-const default_cc_exe = if (is_windows) "cc.exe" else "cc";
-
 pub const CCPrintFileNameOptions = struct {
     allocator: *Allocator,
     search_basename: []const u8,
@@ -553,22 +563,33 @@ pub const CCPrintFileNameOptions = struct {
 fn ccPrintFileName(args: CCPrintFileNameOptions) ![:0]u8 {
     const allocator = args.allocator;
 
-    const cc_exe = std.os.getenvZ("CC") orelse default_cc_exe;
-    const arg1 = try std.fmt.allocPrint(allocator, "-print-file-name={s}", .{args.search_basename});
-    defer allocator.free(arg1);
-    const argv = [_][]const u8{ cc_exe, arg1 };
-
+    // Detect infinite loops.
     var env_map = try std.process.getEnvMap(allocator);
     defer env_map.deinit();
+    const skip_cc_env_var = if (env_map.get(inf_loop_env_key)) |phase| blk: {
+        if (std.mem.eql(u8, phase, "1")) {
+            try env_map.put(inf_loop_env_key, "2");
+            break :blk true;
+        } else {
+            return error.ZigIsTheCCompiler;
+        }
+    } else blk: {
+        try env_map.put(inf_loop_env_key, "1");
+        break :blk false;
+    };
 
-    // Detect infinite loops.
-    const inf_loop_env_key = "ZIG_IS_DETECTING_LIBC_PATHS";
-    if (env_map.get(inf_loop_env_key) != null) return error.ZigIsTheCCompiler;
-    try env_map.put(inf_loop_env_key, "1");
+    var argv = std.ArrayList([]const u8).init(allocator);
+    defer argv.deinit();
+
+    const arg1 = try std.fmt.allocPrint(allocator, "-print-file-name={s}", .{args.search_basename});
+    defer allocator.free(arg1);
+
+    try appendCcExe(&argv, skip_cc_env_var);
+    try argv.append(arg1);
 
     const exec_res = std.ChildProcess.exec(.{
         .allocator = allocator,
-        .argv = &argv,
+        .argv = argv.items,
         .max_output_bytes = 1024 * 1024,
         .env_map = &env_map,
         // Some C compilers, such as Clang, are known to rely on argv[0] to find the path
@@ -586,11 +607,11 @@ fn ccPrintFileName(args: CCPrintFileNameOptions) ![:0]u8 {
     }
     switch (exec_res.term) {
         .Exited => |code| if (code != 0) {
-            printVerboseInvocation(&argv, args.search_basename, args.verbose, exec_res.stderr);
+            printVerboseInvocation(argv.items, args.search_basename, args.verbose, exec_res.stderr);
             return error.CCompilerExitCode;
         },
         else => {
-            printVerboseInvocation(&argv, args.search_basename, args.verbose, exec_res.stderr);
+            printVerboseInvocation(argv.items, args.search_basename, args.verbose, exec_res.stderr);
             return error.CCompilerCrashed;
         },
     }
@@ -659,3 +680,23 @@ fn fillSearch(search_buf: *[2]Search, sdk: *ZigWindowsSDK) []Search {
     }
     return search_buf[0..search_end];
 }
+
+const inf_loop_env_key = "ZIG_IS_DETECTING_LIBC_PATHS";
+
+fn appendCcExe(args: *std.ArrayList([]const u8), skip_cc_env_var: bool) !void {
+    const default_cc_exe = if (is_windows) "cc.exe" else "cc";
+    try args.ensureUnusedCapacity(1);
+    if (skip_cc_env_var) {
+        args.appendAssumeCapacity(default_cc_exe);
+        return;
+    }
+    const cc_env_var = std.os.getenvZ("CC") orelse {
+        args.appendAssumeCapacity(default_cc_exe);
+        return;
+    };
+    // Respect space-separated flags to the C compiler.
+    var it = std.mem.tokenize(cc_env_var, " ");
+    while (it.next()) |arg| {
+        try args.append(arg);
+    }
+}