編譯器前端的核心任務是根據程式語言的**文法**將原始碼轉換為抽象語法樹（AST）。文法通常以**巴科斯-諾爾範式（BNF）** 或其擴展形式（EBNF）定義。本文整理了簡化版 C 語言的完整文法產生式，涵蓋從程式結構到運算式優先序的各層級規則，適合編譯原理學習者參考。
→ 或 ::=：產生式定義。|：選擇（或）。IDENTIFIER, CONSTANT, ';', '{' 等。program, expression 等。
program → external_declaration
| program external_declaration
external_declaration → function_definition
| declaration
function_definition → type_specifier declarator compound_statement
type_specifier → VOID | CHAR | INT | FLOAT
| struct_or_union_specifier
| enum_specifier
| TYPEDEF_NAME
declarator → pointer direct_declarator
| direct_declarator
pointer → '*'
| '*' pointer
direct_declarator → IDENTIFIER
| direct_declarator '[' ']'
| direct_declarator '[' constant_expression ']'
| IDENTIFIER '(' parameter_list ')'
| IDENTIFIER '(' ')'
| direct_declarator ',' identifier_list
identifier_list → IDENTIFIER
| identifier_list ',' IDENTIFIER
parameter_list → parameter_declaration
| parameter_list ',' parameter_declaration
parameter_declaration → declaration_specifiers IDENTIFIER
compound_statement → '{' '}'
| '{' statement_list '}'
| '{' declaration_list statement_list '}'
declaration_list → declaration
| declaration_list declaration
statement_list → statement
| statement_list statement
statement → compound_statement
| expression_statement
| selection_statement
| iteration_statement
| jump_statement
| labeled_statement
expression_statement → ';'
| expression ';'
selection_statement → IF '(' expression ')' statement
| IF '(' expression ')' statement ELSE statement
iteration_statement → WHILE '(' expression ')' statement
| FOR '(' expression_statement expression_statement ')' statement
| FOR '(' expression_statement expression_statement expression ')' statement
jump_statement → CONTINUE ';'
| BREAK ';'
| RETURN ';'
| RETURN expression ';'
labeled_statement → IDENTIFIER ':' statement
| CASE constant_expression ':' statement
| DEFAULT ':' statement
declaration → init_declarator
| init_declarator_list ',' init_declarator
init_declarator → declarator
| declarator '=' initializer
initializer → assignment_expression
| '{' initializer_list '}'
| '{' initializer_list ',' '}'
initializer_list → initializer
| initializer_list ',' initializer
expression → assignment_expression
| expression ',' assignment_expression
assignment_expression → conditional_expression
| unary_expression assignment_operator assignment_expression
conditional_expression → logical_or_expression
| logical_or_expression '?' expression ':' conditional_expression
logical_or_expression → logical_and_expression
| logical_or_expression OR_OP logical_and_expression
logical_and_expression → inclusive_or_expression
| logical_and_expression AND_OP inclusive_or_expression
inclusive_or_expression → exclusive_or_expression
| inclusive_or_expression '|' exclusive_or_expression
exclusive_or_expression → and_expression
| exclusive_or_expression '^' and_expression
and_expression → equality_expression
| and_expression '&' equality_expression
equality_expression → relational_expression
| equality_expression EQ_OP relational_expression
| equality_expression NE_OP relational_expression
relational_expression → shift_expression
| relational_expression '<' shift_expression
| relational_expression '>' shift_expression
| relational_expression LE_OP shift_expression
| relational_expression GE_OP shift_expression
shift_expression → additive_expression
| shift_expression LEFT_OP additive_expression
| shift_expression RIGHT_OP additive_expression
additive_expression → multiplicative_expression
| additive_expression '+' multiplicative_expression
| additive_expression '-' multiplicative_expression
multiplicative_expression → cast_expression
| multiplicative_expression '*' cast_expression
| multiplicative_expression '/' cast_expression
| multiplicative_expression '%' cast_expression
cast_expression → unary_expression
| '(' type_name ')' cast_expression
unary_expression → postfix_expression
| INC_OP unary_expression
| DEC_OP unary_expression
| unary_operator cast_expression
| SIZEOF unary_expression
| SIZEOF '(' type_name ')'
postfix_expression → primary_expression
| postfix_expression '[' expression ']'
| postfix_expression '(' ')'
| postfix_expression '(' argument_expression_list ')'
| postfix_expression '.' IDENTIFIER
| postfix_expression PTR_OP IDENTIFIER
| postfix_expression INC_OP
| postfix_expression DEC_OP
primary_expression → IDENTIFIER
| CONSTANT
| STRING_LITERAL
| '(' expression ')'
argument_expression_list → assignment_expression
| argument_expression_list ',' assignment_expression
unary_operator → '&' | '*' | '+' | '-' | '~' | '!'
assignment_operator → '='
| MUL_ASSIGN | DIV_ASSIGN | MOD_ASSIGN
| ADD_ASSIGN | SUB_ASSIGN
| LEFT_ASSIGN | RIGHT_ASSIGN
| AND_ASSIGN | XOR_ASSIGN | OR_ASSIGN
struct_or_union_specifier → struct_or_union IDENTIFIER '{' struct_declaration_list '}'
| struct_or_union '{' struct_declaration_list '}'
| struct_or_union IDENTIFIER
struct_or_union → STRUCT | UNION
struct_declaration_list → struct_declaration
| struct_declaration_list struct_declaration
struct_declaration → specifier_qualifier_list struct_declarator_list ';'
specifier_qualifier_list → type_specifier specifier_qualifier_list
| type_specifier
| type_qualifier specifier_qualifier_list
| type_qualifier
struct_declarator_list → struct_declarator
| struct_declarator_list ',' struct_declarator
struct_declarator → declarator
| ':' constant_expression
| declarator ':' constant_expression
enum_specifier → ENUM '{' enumerator_list '}'
| ENUM IDENTIFIER '{' enumerator_list '}'
| ENUM IDENTIFIER
enumerator_list → enumerator
| enumerator_list ',' enumerator
enumerator → IDENTIFIER
| IDENTIFIER '=' constant_expression
type_qualifier → CONST | VOLATILE
type_name → specifier_qualifier_list
| specifier_qualifier_list abstract_declarator
abstract_declarator → pointer
| direct_abstract_declarator
| pointer direct_abstract_declarator
direct_abstract_declarator → '(' abstract_declarator ')'
| '[' ']'
| '[' constant_expression ']'
| direct_abstract_declarator '[' ']'
| direct_abstract_declarator '[' constant_expression ']'
| '(' ')'
| '(' parameter_type_list ')'
| direct_abstract_declarator '(' ')'
| direct_abstract_declarator '(' parameter_type_list ')'
storage_class_specifier → TYPEDEF | EXTERN | STATIC | AUTO | REGISTER
program 入口追蹤到 primary_expression，理解層級遞歸結構。additive_expression 左結合）。掌握文法產生式是編譯器前端開發的基石。本文提供的簡化 C 文法涵蓋核心結構，可作為手寫遞歸下降解析器、學習 LR(k) 分析、理解語言設計的優質參考資料。
