Handle fcommon option

  * If `-fno-common` or by default, then put variable into `.bss` section
  * Add `.zero` dhirective

src/as/arch/aarch64/ir_asm_aarch64.c

@@ -65,6 +65,9 @@ bool calc_label_address(uintptr_t start_address, Vector *sections, Table *label_
       case IR_BSS:
         address += ir->bss;
         break;
+      case IR_ZERO:
+        address += ir->zero;
+        break;
       case IR_ALIGN:
         ir->address = address = ALIGN(address, ir->align);
         if ((size_t)ir->align > section->align) {
@@ -263,6 +266,7 @@ bool resolve_relative_address(Vector *sections, Table *label_table, Vector *unre
       case IR_LABEL:
       case IR_DATA:
       case IR_BSS:
+      case IR_ZERO:
       case IR_ALIGN:
         break;
       }
@@ -290,6 +294,14 @@ void emit_irs(Vector *sections) {
       case IR_BSS:
         sec_add_bss(section, ir->bss);
         break;
+      case IR_ZERO:
+        if (section->flag & SF_BSS) {
+          sec_add_bss(section, ir->zero);
+        } else {
+          void *buf = calloc_or_die(ir->zero);
+          sec_add_data(section, buf, ir->zero);
+        }
+        break;
       case IR_ALIGN:
         sec_align_size(section, ir->align);
         break;

src/as/arch/riscv64/ir_asm_riscv64.c

@@ -67,6 +67,9 @@ bool calc_label_address(uintptr_t start_address, Vector *sections, Table *label_
       case IR_BSS:
         address += ir->bss;
         break;
+      case IR_ZERO:
+        address += ir->zero;
+        break;
       case IR_ALIGN:
         ir->address = address = ALIGN(address, ir->align);
         if ((size_t)ir->align > section->align) {
@@ -340,6 +343,7 @@ bool resolve_relative_address(Vector *sections, Table *label_table, Vector *unre
       case IR_LABEL:
       case IR_DATA:
       case IR_BSS:
+      case IR_ZERO:
       case IR_ALIGN:
         break;
       }
@@ -367,6 +371,14 @@ void emit_irs(Vector *sections) {
       case IR_BSS:
         sec_add_bss(section, ir->bss);
         break;
+      case IR_ZERO:
+        if (section->flag & SF_BSS) {
+          sec_add_bss(section, ir->zero);
+        } else {
+          void *buf = calloc_or_die(ir->zero);
+          sec_add_data(section, buf, ir->zero);
+        }
+        break;
       case IR_ALIGN:
         sec_align_size(section, ir->align);
         break;

src/as/arch/x64/ir_asm_x64.c

@@ -66,6 +66,9 @@ bool calc_label_address(uintptr_t start_address, Vector *sections, Table *label_
       case IR_BSS:
         address += ir->bss;
         break;
+      case IR_ZERO:
+        address += ir->zero;
+        break;
       case IR_ALIGN:
         ir->address = address = ALIGN(address, ir->align);
         if ((size_t)ir->align > section->align) {
@@ -259,6 +262,7 @@ bool resolve_relative_address(Vector *sections, Table *label_table, Vector *unre
       case IR_LABEL:
       case IR_DATA:
       case IR_BSS:
+      case IR_ZERO:
       case IR_ALIGN:
         break;
       }
@@ -286,6 +290,14 @@ void emit_irs(Vector *sections) {
       case IR_BSS:
         sec_add_bss(section, ir->bss);
         break;
+      case IR_ZERO:
+        if (section->flag & SF_BSS) {
+          sec_add_bss(section, ir->zero);
+        } else {
+          void *buf = calloc_or_die(ir->zero);
+          sec_add_data(section, buf, ir->zero);
+        }
+        break;
       case IR_ALIGN:
         sec_align_size(section, ir->align);
         break;

src/as/ir_asm.c

@@ -32,6 +32,13 @@ IR *new_ir_bss(size_t size) {
   return ir;
 }
 
+IR *new_ir_zero(size_t size) {
+  IR *ir = calloc_or_die(sizeof(*ir));
+  ir->kind = IR_ZERO;
+  ir->zero = size;
+  return ir;
+}
+
 IR *new_ir_align(int align) {
   IR *ir = calloc_or_die(sizeof(*ir));
   ir->kind = IR_ALIGN;

src/as/ir_asm.h

@@ -55,6 +55,7 @@ enum IrKind {
   IR_CODE,
   IR_DATA,
   IR_BSS,
+  IR_ZERO,
   IR_ALIGN,
   IR_EXPR_BYTE,
   IR_EXPR_SHORT,
@@ -73,6 +74,7 @@ typedef struct {
       int64_t addend;  // Calculated in `resolve_relative_address`
     } expr;
     size_t bss;
+    size_t zero;
     int align;
     int section;
   };
@@ -83,6 +85,7 @@ IR *new_ir_label(const Name *label);
 IR *new_ir_code(const Code *code);
 IR *new_ir_data(const void *data, size_t size);
 IR *new_ir_bss(size_t size);
+IR *new_ir_zero(size_t size);
 IR *new_ir_align(int align);
 IR *new_ir_expr(enum IrKind kind, const Expr *expr);
 

src/as/parse_asm.c

@@ -38,6 +38,7 @@ static const char *kDirectiveTable[] = {
   "section",
   "text",
   "data",
+  "bss",
   "align",
   "p2align",
   "type",
@@ -46,6 +47,7 @@ static const char *kDirectiveTable[] = {
   "long",
   "quad",
   "comm",
+  "zero",
   "globl",
   "local",
   "extern",
@@ -883,6 +885,15 @@ void handle_directive(ParseInfo *info, enum DirectiveType dir) {
     }
     break;
 
+  case DT_ZERO:
+    {
+      int64_t num;
+      if (!immediate(&info->p, &num))
+        parse_error(info, ".zero: number expected");
+      vec_push(irs, new_ir_zero(num));
+    }
+    break;
+
   case DT_TEXT:
     set_current_section(info, kSecText, kSegText, SF_EXECUTABLE);
     break;
@@ -891,6 +902,10 @@ void handle_directive(ParseInfo *info, enum DirectiveType dir) {
     set_current_section(info, kSecData, kSegData, SF_WRITABLE);
     break;
 
+  case DT_BSS:
+    set_current_section(info, kSecBss, kSegBss, SF_BSS | SF_WRITABLE);
+    break;
+
   case DT_ALIGN:
     {
       int64_t align;

src/as/parse_asm.h

@@ -20,6 +20,7 @@ enum DirectiveType {
   DT_SECTION,
   DT_TEXT,
   DT_DATA,
+  DT_BSS,
   DT_ALIGN,
   DT_P2ALIGN,
   DT_TYPE,
@@ -28,6 +29,7 @@ enum DirectiveType {
   DT_LONG,
   DT_QUAD,
   DT_COMM,
+  DT_ZERO,
   DT_GLOBL,
   DT_LOCAL,
   DT_EXTERN,

src/cc/backend/emit_util.c

@@ -244,6 +244,10 @@ static void emit_varinfo(const VarInfo *varinfo, const Initializer *init) {
       _RODATA();
     else
       _DATA();
+  } else {
+    if (!cc_flags.common) {
+      _BSS();
+    }
   }
 
   char *label = fmt_name(name);
@@ -268,7 +272,13 @@ static void emit_varinfo(const VarInfo *varinfo, const Initializer *init) {
       size = 1;
 
     size_t align = align_size(varinfo->type);
-    _COMM(label, size, align);
+    if (cc_flags.common) {
+      _COMM(label, size, align);
+    } else {
+      EMIT_ALIGN(align_size(varinfo->type));
+      EMIT_LABEL(label);
+      _ZERO(num(size));
+    }
   }
 }
 

src/cc/backend/emit_util.h

@@ -59,6 +59,8 @@ bool function_not_returned(FuncBackend *fnbe);
 #define _SECTION(x)    EMIT_ASM(".section", x)
 #define _TEXT()        EMIT_ASM(".text")
 #define _DATA()        EMIT_ASM(".data")
+#define _BSS()         EMIT_ASM(".bss")
+#define _ZERO(x)       EMIT_ASM(".zero", x)
 
 #define EMIT_ALIGN(x)  emit_align_p2(x)
 

src/cc/cc1.c

@@ -45,14 +45,40 @@ static void compile1(FILE *ifp, const char *filename, Vector *decls) {
   parse(decls);
 }
 
+static bool parse_fopt(const char *optarg, bool value) {
+  static const struct {
+    const char *flag_name;
+    off_t flag_offset;
+  } kFlagTable[] = {
+    {"common", offsetof(CcFlags, common)},
+  };
+
+  for (size_t i = 0; i < ARRAY_SIZE(kFlagTable); ++i) {
+    if (strcmp(optarg, kFlagTable[i].flag_name) == 0) {
+      size_t len = strlen(kFlagTable[i].flag_name);
+      if (optarg[len] != '\0')
+        continue;
+      bool *p = (bool*)((char*)&cc_flags + kFlagTable[i].flag_offset);
+      *p = value;
+      return true;
+    }
+  }
+  return false;
+}
+
 int main(int argc, char *argv[]) {
   enum {
-    OPT_WARNING = 128,
+    OPT_FNO = 128,
   };
 
   static const struct option options[] = {
-    {"W", required_argument, OPT_WARNING},
     {"-version", no_argument, 'V'},
+
+    // Sub command
+    {"fno-", required_argument, OPT_FNO},
+    {"f", required_argument},
+    {"W", required_argument},
+
     {NULL},
   };
   int opt;
@@ -61,14 +87,24 @@ int main(int argc, char *argv[]) {
     case 'V':
       show_version("cc1");
       return 0;
-    case OPT_WARNING:
+
+    case 'f':
+    case OPT_FNO:
+      if (!parse_fopt(optarg, opt == 'f')) {
+        // Silently ignored.
+        // fprintf(stderr, "Warning: unknown option for -f: %s\n", optarg);
+      }
+      break;
+
+    case 'W':
       if (strcmp(optarg, "error") == 0) {
         cc_flags.warn_as_error = true;
       } else {
         // Silently ignored.
         // fprintf(stderr, "Warning: unknown option for -W: %s\n", optarg);
       }
       break;
+
     default:
       fprintf(stderr, "Warning: unknown option: %s\n", argv[optind - 1]);
       break;

src/cc/frontend/fe_misc.c

@@ -23,6 +23,7 @@ int compile_error_count;
 
 CcFlags cc_flags = {
   .warn_as_error = false,
+  .common = false,
 };
 
 LoopScope loop_scope;

src/cc/frontend/fe_misc.h

@@ -28,6 +28,7 @@ enum ParseErrorLevel {
 
 typedef struct {
   bool warn_as_error;  // Treat warnings as errors
+  bool common;
 } CcFlags;
 
 extern CcFlags cc_flags;