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+# C Grammar
+
+
+## Notation
+
+* `'A'`: Terminal symbol
+* `A`: Non-terminal symbol
+* `A / B`: A or B
+* `A?`: Optional A
+* `{ A }+`: 1 or more repetitions of A
+* `{ A }*`: 0 or more repetitions of A
+* `{ A | S }`: Repetition of A separated by S
+ * Note that trailing S is not allowed.
+* `( A )`: Grouping
+* `# ...`: Additional constraints
+
+
+## Expressions
+
+```
+primary-expr:
+ identifier
+ constant
+ string-literal
+ '(' expr ')'
+ generic-selection
+
+generic-selection:
+ '_Generic' '(' assignment-expr ',' generic-assoc-list ')'
+
+generic-assoc-list:
+ { generic-association | ',' }*
+
+generic-association:
+ type-name ':' assignment-expr
+ 'default' ':' assignment-expr
+
+postfix-expr:
+ postfix-expr-stem { postfix-expr-postfix }*
+
+postfix-expr-stem:
+ primary-expr
+ compound-literal
+
+postfix-expr-postfix:
+ '[' expr ']'
+ '(' argument-expr-list? ')'
+ '.' identifier
+ '->' identifier
+ '++'
+ '--'
+
+argument-expr-list:
+ { assignment-expr | ',' }+
+
+compound-literal:
+ '(' storage-class-specifiers? type-name ')' braced-initializer
+
+storage-class-specifiers:
+ { storage-class-specifier }+
+
+unary-expr:
+ postfix-expr
+ '++' unary-expr
+ '--' unary-expr
+ unary-operator cast-expr
+ 'sizeof' unary-expr
+ 'sizeof' '(' type-name ')'
+ 'alignof' '(' type-name ')'
+
+unary-operator:
+ '&'
+ '*'
+ '+'
+ '-'
+ '~'
+ '!'
+
+cast-expr:
+ unary-expr
+ '(' type-name ')' cast-expr
+
+multiplicative-expr:
+ cast-expr { ( '*' / '/' / '%' ) cast-expr }*
+
+additive-expr:
+ multiplicative-expr { ( '+' / '-' ) multiplicative-expr }*
+
+shift-expr:
+ additive-expr { ( '<<' / '>>' ) additive-expr }*
+
+relational-expr:
+ shift-expr { ( '<' / '>' / '<=' / '>=' ) shift-expr }*
+
+equality-expr:
+ relational-expr { ( '==' / '!=' ) relational-expr }*
+
+bitwise-and-expr:
+ equality-expr { '&' equality-expr }*
+
+bitwise-xor-expr:
+ bitwise-and-expr { '^' bitwise-and-expr }*
+
+bitwise-or-expr:
+ bitwise-xor-expr { '|' bitwise-xor-expr }*
+
+logical-and-expr:
+ bitwise-or-expr { '&&' bitwise-or-expr }*
+
+logical-or-expr:
+ logical-and-expr { '||' logical-and-expr }*
+
+conditional-expr:
+ logical-or-expr ( '?' expr ':' conditional-expr )?
+
+assignment-expr:
+ conditional-expr
+ unary-expr assignment-operator assignment-expr
+
+assignment-operator:
+ '='
+ '*='
+ '/='
+ '%='
+ '+='
+ '-='
+ '<<='
+ '>>='
+ '&='
+ '^='
+ '|='
+
+expr:
+ assignment-expr { ',' assignment-expr }*
+
+constant-expr:
+ conditional-expr
+```
+
+## Declarations
+
+```
+declaration:
+ static_assert-declaration
+ attribute-specifier-sequence ';'
+ attribute-specifier-sequence declaration-specifiers init-declarator-list ';'
+ declaration-specifiers init-declarator-list ';'
+
+declaration-specifiers:
+ { declaration-specifier }+ attribute-specifier-sequence?
+
+declaration-specifier:
+ storage-class-specifier
+ type-specifier-qualifier
+ function-specifier
+
+init-declarator-list:
+ { init-declarator | ',' }+
+
+init-declarator:
+ declarator ( '=' initializer )?
+
+storage-class-specifier:
+ 'auto'
+ 'constexpr'
+ 'extern'
+ 'register'
+ 'static'
+ 'thread_local'
+ 'typedef'
+
+type-specifier:
+ 'void'
+ 'char'
+ 'short'
+ 'int'
+ 'long'
+ 'float'
+ 'double'
+ 'signed'
+ 'unsigned'
+ '_BitInt' '(' constant-expr ')'
+ 'bool'
+ '_Complex'
+ '_Decimal32'
+ '_Decimal64'
+ '_Decimal128'
+ atomic-type-specifier
+ struct-or-union-specifier
+ enum-specifier
+ typeof-specifier
+ typedef-name
+
+struct-or-union-specifier:
+ struct-or-union attribute-specifier-sequence? identifier? '{' member-declaration-list '}'
+ struct-or-union attribute-specifier-sequence? identifier
+
+struct-or-union:
+ 'struct'
+ 'union'
+
+member-declaration-list:
+ { member-declaration }+
+
+member-declaration:
+ attribute-specifier-sequence? specifier-qualifier-list member-declaration-list? ';'
+ static_assert-declaration
+
+specifier-qualifier-list:
+ { type-specifier-qualifier }+ attribute-specifier-sequence?
+
+type-specifier-qualifier:
+ type-specifier
+ type-qualifier
+ alignment-specifier
+
+member-declarator-list:
+ { member-declarator | ',' }+
+
+member-declarator:
+ declarator
+ declarator? ':' constant-expr
+
+enum-specifier:
+ 'enum' attribute-specifier-sequence? identifier? enum-type-specifier? '{' enumerator-list ','? '}'
+ 'enum' identifier enum-type-specifier?
+
+enumerator-list:
+ { enumerator | ',' }+
+
+enumerator:
+ enumeration-constant attribute-specifier-sequence? ( '=' constant-expr )?
+
+enum-type-specifier:
+ ':' specifier-qualifier-list
+
+atomic-type-specifier:
+ '_Atomic' '(' type-name ')'
+
+typeof-specifier:
+ ( 'typeof' / 'typeof_unqual' ) '(' typeof-specifier-argument ')'
+
+typeof-specifier-argument:
+ expr
+ type-name
+
+type-qualifier:
+ 'const'
+ 'restrict'
+ 'volatile'
+ '_Atomic'
+
+function-specifier:
+ 'inline'
+ '_Noreturn'
+
+alignment-specifier:
+ 'alignas' '(' ( type-name / constant-expr ) ')'
+
+declarator:
+ pointer? direct-declarator
+
+direct-declarator:
+ identifier attribute-specifier-sequence?
+ '(' declarator ')'
+ array-declarator attribute-specifier-sequence?
+ function-declarator attribute-specifier-sequence?
+
+array-declarator:
+ direct-declarator '[' type-qualifier-list? assignment-expr? ']'
+ direct-declarator '[' 'static' type-qualifier-list? assignment-expr ']'
+ direct-declarator '[' type-qualifier-list 'static' assignment-expr ']'
+ direct-declarator '[' type-qualifier-list? '*' ']'
+
+function-declarator:
+ direct-declarator '(' parameter-type-list? ')'
+
+pointer:
+ { '*' attribute-specifier-sequence? type-qualifier-list? }+
+
+type-qualifier-list:
+ { type-qualifier }+
+
+parameter-type-list:
+ parameter-list
+ parameter-list ',' '...'
+ '...'
+
+parameter-list:
+ { parameter-declaration | ',' }+
+
+parameter-declaration:
+ attribute-specifier-sequence? declaration-specifiers ( declarator / abstract-declarator? )
+
+type-name:
+ specifier-qualifier-list abstract-declarator?
+
+abstract-declarator:
+ pointer
+ pointer? direct-abstract-declarator
+
+direct-abstract-declarator:
+ '(' abstract-declarator ')'
+ array-abstract-declarator attribute-specifier-sequence?
+ function-abstract-declarator attribute-specifier-sequence?
+
+array-abstract-declarator:
+ direct-abstract-declarator? '[' type-qualifier-list? assignment-expr? ']'
+ direct-abstract-declarator? '[' 'static' type-qualifier-list? assignment-expr ']'
+ direct-abstract-declarator? '[' type-qualifier-list 'static' assignment-expr ']'
+ direct-abstract-declarator? '[' '*' ']'
+
+function-abstract-declarator:
+ direct-abstract-declarator? '(' parameter-type-list? ')'
+
+typedef-name:
+ identifier
+
+braced-initializer:
+ '{' ( initializer-list ','? )? '}'
+
+initializer:
+ assignment-expr
+ braced-initializer
+
+initializer-list:
+ { designation? initializer | ',' }+
+
+designation:
+ designator-list '='
+
+designator-list:
+ { designator }+
+
+designator:
+ '[' constant-expr ']'
+ '.' identifier
+
+static_assert-declaration:
+ 'static_assert' '(' constant-expr ( ',' string-literal )? ')' ';'
+
+attribute-specifier-sequence:
+ { attribute-specifier }+
+
+attribute-specifier:
+ '[' '[' attribute-list ']' ']'
+
+attribute-list:
+ { attribute? | ',' }
+
+attribute:
+ attribute-token attribute-argument-clause?
+
+attribute-token:
+ identifier ( '::' identifier )?
+
+attribute-argument-clause:
+ '(' balanced-token-sequence ')'
+
+balanced-token-sequence:
+ { balanced-token }+
+
+balanced-token:
+ '(' balanced-token-sequence? ')'
+ '[' balanced-token-sequence? ']'
+ '{' balanced-token-sequence? '}'
+ any token other than a parenthesis, a bracket, or a brace
+```
+
+
+## Statements
+
+```
+stmt:
+ labeled-stmt
+ unlabaled-stmt
+
+unlabaled-stmt:
+ expr-stmt
+ attribute-specifier-sequence? ( primary-block / jump-stmt )
+
+primary-block:
+ compound-stmt
+ selection-stmt
+ iteration-stmt
+
+label:
+ attribute-specifier-sequence? identifier ':'
+ attribute-specifier-sequence? 'case' constant-expr ':'
+ attribute-specifier-sequence? 'default' ':'
+
+labeled-stmt:
+ label stmt
+
+compound-stmt:
+ '{' block-item-list? '}'
+
+block-item-list:
+ { block-item }+
+
+expr-stmt:
+ attribute-specifier-sequence? expr? ';'
+
+selection-stmt:
+ 'if' '(' expr ')' stmt ( 'else' stmt )?
+ 'switch' '(' expr ')' stmt
+
+iteration-stmt:
+ 'while' '(' expr ')' stmt
+ 'do' stmt 'while' '(' expr ')' ';'
+ 'for' '(' expr? ';' expr? ';' expr? ')' stmt
+ 'for' '(' declaration expr? ';' expr? ')' stmt
+
+jump-stmt:
+ 'goto' identifier ';'
+ 'continue' ';'
+ 'break' ';'
+ 'return' expr? ';'
+```
+
+
+## External definitions
+
+```
+translation-unit:
+ { external-declaration }+
+
+external-declaration:
+ function-definition
+ declaration
+
+external-declaration:
+ static_assert-declaration
+ attribute-specifier-sequence ';'
+ attribute-specifier-sequence function-definition-or-declaration-rest
+ function-definition-or-declaration-rest
+
+function-definition-or-declaration-rest:
+ declaration-specifiers init-declarator-list ';'
+ declaration-specifiers init-declarator-list compound-stmt
+ # Each item of init-declarator-list must not have initializer.
+ # The length of init-declarator-list must be one.
+```
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