feat(cmd): GOOS-aware headers, audit battery shapes and semicolon spacing

Assisted-by: GLM 5.3 Flash

cmd/gasm/main.go

@@ -486,7 +486,7 @@ hover, document symbols, diagnostics and semantic-token highlighting.
 }
 
 func cmdAsm(args []string) int {
-	fs := newCommand("asm", "gasm asm [--format raw|elf|goobj] [-I dir] [-p pkg] [-GOARCH arch] [-o out] <file>", `
+	fs := newCommand("asm", "gasm asm [--format raw|elf|goobj] [-I dir] [-p pkg] [-GOARCH arch] [-GOOS os] [-o out] <file>", `
 	Assemble FILE without the Go toolchain: every TEXT function is encoded to
 	machine code and printed as a hex dump.  Supported architectures: amd64
 	(including VEX/AVX2 and EVEX/AVX-512), arm64 (AArch64 integer, FP,
@@ -507,18 +507,22 @@ and the format version from go version).
 A file that includes go_asm.h gets that header generated automatically from
 the package it lives in (the .go files beside it, type-checked for the
 target architecture, the toolchain's own defines), so GOROOT assembly
-assembles without a compiler.  A package that has no Go files for the
-target or does not type-check is a hard error naming the package.
+assembles without a compiler.  -GOOS selects the type-checking GOOS for
+that header: a GOOS-specific file (sys_darwin_arm64.s) needs its platform's
+defines, which a header from the ambient GOOS silently omits.  A package
+that has no Go files for the target or does not type-check is a hard error
+naming the package.
 `)
 	out := fs.String("o", "", "write the output to this file")
 	format := fs.String("format", "raw", "output format: raw (concatenated image), elf or goobj (Go object)")
 	pkg := fs.String("p", "", "package path for --format goobj (qualifies the exported symbols)")
 	archName := fs.String("GOARCH", "", "target architecture: amd64, arm64, riscv64 or loong64 (overrides the file-name suffix)")
+	goosName := fs.String("GOOS", "", "operating system for go_asm.h generation: a GOOS go/build recognises (default: the host's)")
 	var dirs includeDirs
 	fs.Var(&dirs, "I", "directory to search for #include files (may be repeated)")
 	fs.Parse(args)
 	if fs.NArg() != 1 {
-		fmt.Fprintln(os.Stderr, "usage: gasm asm [--format raw|elf|goobj] [-I dir] [-p pkg] [-GOARCH arch] [-o out] <file>")
+		fmt.Fprintln(os.Stderr, "usage: gasm asm [--format raw|elf|goobj] [-I dir] [-p pkg] [-GOARCH arch] [-GOOS os] [-o out] <file>")
 		return 2
 	}
 	// The format is validated before anything else, so a bogus value exits 2
@@ -539,6 +543,15 @@ target or does not type-check is a hard error naming the package.
 		}
 		targetArch = a
 	}
+	goos := ""
+	if *goosName != "" {
+		g, err := resolveGOOS(*goosName)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "gasm asm: %v\n", err)
+			return 2
+		}
+		goos = g
+	}
 	src, err := readSource(path)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "gasm:", err)
@@ -553,7 +566,7 @@ target or does not type-check is a hard error naming the package.
 	// A go_asm.h that already resolves (placed by hand, or passed with -I)
 	// is left alone.
 	if needsGoAsmHeader(src) && !goAsmHeaderResolved(filepath.Dir(path), dirs) {
-		hdrDir, cleanup, err := ensureGoAsmHeader(path, targetArch, nil)
+		hdrDir, cleanup, err := ensureGoAsmHeader(path, targetArch, goos, nil)
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "gasm asm:", err)
 			return 1