zig run/cc: recognize "-x language"

This commit adds support for "-x language" for a couple of hand-picked
supported languages. There is no reason the list of supported languages
to not grow (e.g. add "c-header"), but I'd like to keep it small at the
start.

Alternative 1
-------------

I first tried to add a new type "Language", and then add that to the
`CSourceFile`. But oh boy what a change it turns out to be. So I am
keeping myself tied to FileExt and see what you folks think.

Alternative 2
-------------

I tried adding `Language: ?[]const u8` to `CSourceFile`. However, the
language/ext, whatever we want to call it, still needs to be interpreted
in the main loop: one kind of handling for source files, other kind of
handling for everything else.

Test case
---------

*standalone.c*

    #include <iostream>

    int main() {
        std::cout << "elho\n";
    }

Compile and run:

    $ ./zig run -x c++ -lc++ standalone.c
    elho
    $ ./zig c++ -x c++ standalone.c -o standalone && ./standalone
    elho

Fixes #10915

1 files changed, 50 insertions, 31 deletions

diff --git a/src/main.zig b/src/main.zig
index f203bad968..2e97cc0214 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -391,6 +391,7 @@ const usage_build_generic =
     \\  -mcmodel=[default|tiny|   Limit range of code and data virtual addresses
     \\            small|kernel|
     \\            medium|large]
+    \\  -x language               Treat subsequent input files as having type <language>
     \\  -mred-zone                Force-enable the "red-zone"
     \\  -mno-red-zone             Force-disable the "red-zone"
     \\  -fomit-frame-pointer      Omit the stack frame pointer
@@ -913,6 +914,7 @@ fn buildOutputType(
             var cssan = ClangSearchSanitizer.init(gpa, &clang_argv);
             defer cssan.map.deinit();
 
+            var file_ext: ?Compilation.FileExt = null;
             args_loop: while (args_iter.next()) |arg| {
                 if (mem.startsWith(u8, arg, "@")) {
                     // This is a "compiler response file". We must parse the file and treat its
@@ -1401,6 +1403,15 @@ fn buildOutputType(
                         try clang_argv.append(arg);
                     } else if (mem.startsWith(u8, arg, "-I")) {
                         try cssan.addIncludePath(.I, arg, arg[2..], true);
+                    } else if (mem.eql(u8, arg, "-x")) {
+                        const lang = args_iter.nextOrFatal();
+                        if (mem.eql(u8, lang, "none")) {
+                            file_ext = null;
+                        } else if (Compilation.LangToExt.get(lang)) |got_ext| {
+                            file_ext = got_ext;
+                        } else {
+                            fatal("language not recognized: '{s}'", .{lang});
+                        }
                     } else if (mem.startsWith(u8, arg, "-mexec-model=")) {
                         wasi_exec_model = std.meta.stringToEnum(std.builtin.WasiExecModel, arg["-mexec-model=".len..]) orelse {
                             fatal("expected [command|reactor] for -mexec-mode=[value], found '{s}'", .{arg["-mexec-model=".len..]});
@@ -1408,22 +1419,21 @@ fn buildOutputType(
                     } else {
                         fatal("unrecognized parameter: '{s}'", .{arg});
                     }
-                } else switch (Compilation.classifyFileExt(arg)) {
-                    .object, .static_library, .shared_library => {
-                        try link_objects.append(.{ .path = arg });
-                    },
-                    .assembly, .c, .cpp, .h, .ll, .bc, .m, .mm, .cu => {
+                } else switch (file_ext orelse
+                    Compilation.classifyFileExt(arg)) {
+                    .object, .static_library, .shared_library => try link_objects.append(.{ .path = arg }),
+                    .assembly, .assembly_with_cpp, .c, .cpp, .h, .ll, .bc, .m, .mm, .cu => {
                         try c_source_files.append(.{
                             .src_path = arg,
                             .extra_flags = try arena.dupe([]const u8, extra_cflags.items),
+                            // duped when parsing the args.
+                            .ext = file_ext,
                         });
                     },
                     .zig => {
                         if (root_src_file) |other| {
                             fatal("found another zig file '{s}' after root source file '{s}'", .{ arg, other });
-                        } else {
-                            root_src_file = arg;
-                        }
+                        } else root_src_file = arg;
                     },
                     .def, .unknown => {
                         fatal("unrecognized file extension of parameter '{s}'", .{arg});
@@ -1464,6 +1474,7 @@ fn buildOutputType(
             var needed = false;
             var must_link = false;
             var force_static_libs = false;
+            var file_ext: ?Compilation.FileExt = null;
             while (it.has_next) {
                 it.next() catch |err| {
                     fatal("unable to parse command line parameters: {s}", .{@errorName(err)});
@@ -1484,32 +1495,39 @@ fn buildOutputType(
                     .asm_only => c_out_mode = .assembly, // -S
                     .preprocess_only => c_out_mode = .preprocessor, // -E
                     .emit_llvm => emit_llvm = true,
+                    .x => {
+                        const lang = mem.sliceTo(it.only_arg, 0);
+                        if (mem.eql(u8, lang, "none")) {
+                            file_ext = null;
+                        } else if (Compilation.LangToExt.get(lang)) |got_ext| {
+                            file_ext = got_ext;
+                        } else {
+                            fatal("language not recognized: '{s}'", .{lang});
+                        }
+                    },
                     .other => {
                         try clang_argv.appendSlice(it.other_args);
                     },
-                    .positional => {
-                        const file_ext = Compilation.classifyFileExt(mem.sliceTo(it.only_arg, 0));
-                        switch (file_ext) {
-                            .assembly, .c, .cpp, .ll, .bc, .h, .m, .mm, .cu => {
-                                try c_source_files.append(.{ .src_path = it.only_arg });
-                            },
-                            .unknown, .shared_library, .object, .static_library => {
-                                try link_objects.append(.{
-                                    .path = it.only_arg,
-                                    .must_link = must_link,
-                                });
-                            },
-                            .def => {
-                                linker_module_definition_file = it.only_arg;
-                            },
-                            .zig => {
-                                if (root_src_file) |other| {
-                                    fatal("found another zig file '{s}' after root source file '{s}'", .{ it.only_arg, other });
-                                } else {
-                                    root_src_file = it.only_arg;
-                                }
-                            },
-                        }
+                    .positional => switch (file_ext orelse
+                        Compilation.classifyFileExt(mem.sliceTo(it.only_arg, 0))) {
+                        .assembly, .assembly_with_cpp, .c, .cpp, .ll, .bc, .h, .m, .mm, .cu => {
+                            try c_source_files.append(.{
+                                .src_path = it.only_arg,
+                                .ext = file_ext, // duped while parsing the args.
+                            });
+                        },
+                        .unknown, .shared_library, .object, .static_library => try link_objects.append(.{
+                            .path = it.only_arg,
+                            .must_link = must_link,
+                        }),
+                        .def => {
+                            linker_module_definition_file = it.only_arg;
+                        },
+                        .zig => {
+                            if (root_src_file) |other| {
+                                fatal("found another zig file '{s}' after root source file '{s}'", .{ it.only_arg, other });
+                            } else root_src_file = it.only_arg;
+                        },
                     },
                     .l => {
                         // -l
@@ -4860,6 +4878,7 @@ pub const ClangArgIterator = struct {
         o,
         c,
         m,
+        x,
         other,
         positional,
         l,