diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/Arithmetic.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/Arithmetic.g4
new file mode 100644
index 0000000000..1ff5215c3a
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/Arithmetic.g4
@@ -0,0 +1,10 @@
+grammar Arithmetic;
+prog : expr EOF ;
+expr
+    : expr op=('*'|'/') expr   # MulDiv
+    | expr op=('+'|'-') expr   # AddSub
+    | INT                      # Int
+    | '(' expr ')'             # Parens
+    ;
+INT: [0-9]+;
+WS: [ \t\r\n]+ -> skip;
\ No newline at end of file
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/CSVFlexible.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/CSVFlexible.g4
new file mode 100644
index 0000000000..0be6d36e86
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/CSVFlexible.g4
@@ -0,0 +1,8 @@
+grammar CSVFlexible;
+file : row+ EOF ;
+row : field (',' field)* NEWLINE ;
+field : TEXT | STRING ;
+TEXT : ~[\r\n,"]+ ;
+STRING : '"' ('""'|~'"')* '"' ;
+NEWLINE : ('\r'? '\n')+ ;
+WS : [ \t]+ -> skip ;
\ No newline at end of file
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/JSONMini.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/JSONMini.g4
new file mode 100644
index 0000000000..bd48f6677a
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/JSONMini.g4
@@ -0,0 +1,19 @@
+grammar JSONMini;
+json : value EOF ;
+value
+    : STRING
+    | NUMBER
+    | object
+    | array
+    | 'true'
+    | 'false'
+    | 'null'
+    ;
+object : '{' pair (',' pair)* '}' | '{' '}' ;
+pair : STRING ':' value ;
+array : '[' value (',' value)* ']' | '[' ']' ;
+STRING : '"' (~['"'\\] | '\\' .)* '"' ;
+NUMBER : '-'? INT ('.' [0-9]+)? EXP? ;
+fragment INT : '0' | [1-9] [0-9]* ;
+fragment EXP : [Ee] [+-]? [0-9]+ ;
+WS : [ \t\r\n]+ -> skip ;
\ No newline at end of file
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniConfig.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniConfig.g4
new file mode 100644
index 0000000000..989671be9a
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniConfig.g4
@@ -0,0 +1,8 @@
+grammar MiniConfig;
+config : (pair | section)* EOF ;
+section : '[' NAME ']' (pair)* ;
+pair : NAME '=' VALUE NEWLINE? ;
+NAME : [a-zA-Z_][a-zA-Z0-9_]* ;
+VALUE : ~[\r\n]+ ;
+NEWLINE : ('\r'? '\n')+ ;
+WS : [ \t]+ -> skip ;
\ No newline at end of file
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniMarkdown.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniMarkdown.g4
new file mode 100644
index 0000000000..b00c2ea572
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniMarkdown.g4
@@ -0,0 +1,13 @@
+grammar MiniMarkdown;
+doc : element+ EOF ;
+element
+    : heading
+    | bold
+    | text
+    ;
+heading : '#' WS? TEXT NEWLINE ;
+bold : '**' TEXT '**' ;
+text : TEXT ;
+TEXT : ~[\r\n#*]+ ;
+NEWLINE : ('\r'? '\n')+ ;
+WS : [ \t]+ -> skip ;
\ No newline at end of file
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniQuery.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniQuery.g4
new file mode 100644
index 0000000000..1fb86c29e8
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr4_fixed_grammars/MiniQuery.g4
@@ -0,0 +1,19 @@
+grammar MiniQuery;
+query : 'SELECT' columns 'FROM' table ('WHERE' condition)? EOF ;
+columns : '*' | ID (',' ID)* ;
+table : ID ;
+condition : expr ;
+expr
+    : ID OP value
+    | expr AND expr
+    | expr OR expr
+    | '(' expr ')'
+    ;
+value : STRING | NUMBER ;
+ID : [a-zA-Z_][a-zA-Z0-9_]* ;
+STRING : '\'' (~['\\\r\n])* '\'' ;
+NUMBER : [0-9]+ ;
+AND : 'AND' ;
+OR : 'OR' ;
+OP : '=' | '<>' | '<' | '>' | '<=' | '>=' ;
+WS : [ \t\r\n]+ -> skip ;
\ No newline at end of file
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/Arithmetic.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/Arithmetic.g4
new file mode 100644
index 0000000000..55a6946130
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/Arithmetic.g4
@@ -0,0 +1,7 @@
+grammar Arithmetic;
+expr: expr op=('*'|'/') expr   # MulDiv
+    | expr op=('+'|'-') expr   # AddSub
+    | INT                      # Int
+    | '(' expr ')'             # Parens ;
+INT: [0-9]+;
+WS: [ \t\r\n]+ -> skip;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/BooleanExpr.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/BooleanExpr.g4
new file mode 100644
index 0000000000..6d6c211d72
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/BooleanExpr.g4
@@ -0,0 +1,11 @@
+grammar BooleanExpr;
+expr: expr AND expr
+    | expr OR expr
+    | NOT expr
+    | '(' expr ')'
+    | BOOL ;
+AND: 'AND';
+OR: 'OR';
+NOT: 'NOT';
+BOOL: 'TRUE' | 'FALSE';
+WS: [ \t\r\n]+ -> skip;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/CSVFlexible.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/CSVFlexible.g4
new file mode 100644
index 0000000000..2e8cd7abc0
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/CSVFlexible.g4
@@ -0,0 +1,8 @@
+grammar CSVFlexible;
+file: row+ ;
+row: value (',' value)* NEWLINE ;
+value: QUOTED | TEXT? ;
+TEXT: ~[,"\r\n]+ ;
+QUOTED: '"' (~["\r\n] | '""')* '"' ;
+NEWLINE: '\r'? '\n' ;
+WS: [ \t]+ -> skip ;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/JSONMini.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/JSONMini.g4
new file mode 100644
index 0000000000..b1a66a665b
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/JSONMini.g4
@@ -0,0 +1,10 @@
+grammar JSONMini;
+json: value ;
+value: STRING | NUMBER | obj | array | 'true' | 'false' | 'null' ;
+obj: '{' pair (',' pair)* '}' ;
+pair: STRING ':' value ;
+array: '[' value (',' value)* ']' ;
+STRING: '"' (~["\\] | '\\' .)* '"' ;
+NUMBER: '-'? INT ('.' [0-9]+)? ;
+fragment INT: '0' | [1-9][0-9]* ;
+WS: [ \t\r\n]+ -> skip ;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniConfig.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniConfig.g4
new file mode 100644
index 0000000000..fcb87c589e
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniConfig.g4
@@ -0,0 +1,8 @@
+grammar MiniConfig;
+config: (section | pair)* EOF;
+section: '[' NAME ']' ;
+pair: NAME '=' VALUE ;
+NAME: [a-zA-Z_][a-zA-Z0-9_]* ;
+VALUE: ~[\r\n#;]+ ;
+WS: [ \t\r\n]+ -> skip ;
+COMMENT: ('#'|';').*? -> skip ;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniMarkdown.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniMarkdown.g4
new file mode 100644
index 0000000000..3817ef7d53
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniMarkdown.g4
@@ -0,0 +1,8 @@
+grammar MiniMarkdown;
+doc: (heading | bold | text)+ ;
+heading: '#' WS? TEXT NL ;
+bold: '**' TEXT '**' ;
+text: TEXT NL? ;
+TEXT: ~[\r\n#*]+ ;
+WS: [ \t]+ -> skip ;
+NL: '\r'? '\n' ;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniQuery.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniQuery.g4
new file mode 100644
index 0000000000..811dcfe57a
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/MiniQuery.g4
@@ -0,0 +1,12 @@
+grammar MiniQuery;
+query: 'SELECT' columns 'FROM' table ('WHERE' condition)? EOF ;
+columns: '*' | column (',' column)* ;
+column: ID ;
+table: ID ;
+condition: column op value ;
+op: '=' | '<' | '>' ;
+value: STRING | NUMBER ;
+ID: [a-zA-Z_][a-zA-Z0-9_]* ;
+STRING: '\'' (~['\r\n])* '\'' ;
+NUMBER: [0-9]+ ;
+WS: [ \t\r\n]+ -> skip ;
diff --git a/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/UnitExpr.g4 b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/UnitExpr.g4
new file mode 100644
index 0000000000..cabe063ee3
--- /dev/null
+++ b/runtime-testsuite/test/org/antlr/v4/test/runtime/antlr_grammars/UnitExpr.g4
@@ -0,0 +1,5 @@
+grammar UnitExpr;
+expr: NUMBER UNIT ;
+NUMBER: [0-9]+ ('.' [0-9]+)? ;
+UNIT: [a-zA-Z/_]+ ;
+WS: [ \t\r\n]+ -> skip ;
diff --git a/tool/resources/org/antlr/v4/tool/templates/codegen/Cpp/Cpp.stg b/tool/resources/org/antlr/v4/tool/templates/codegen/Cpp/Cpp.stg
index e557fc811d..f1cc57f955 100644
--- a/tool/resources/org/antlr/v4/tool/templates/codegen/Cpp/Cpp.stg
+++ b/tool/resources/org/antlr/v4/tool/templates/codegen/Cpp/Cpp.stg
@@ -272,13 +272,13 @@ void <r.factory.grammar.name>::<r.name>Action(<r.ctxType> *context, size_t actio
 >>
 
 RuleSempredFunctionHeader(r, actions) ::= <<
-bool <r.name>Sempred(<r.ctxType> *_localctx, size_t predicateIndex);
+bool <r.name>Sempred([[maybe_unused]] <r.ctxType> *_localctx, size_t predicateIndex);
 >>
 
 RuleSempredFunction(r, actions) ::= <<
 <! Called for both lexer and parser. But only one of them is actually available. Testing for the parser directly
    generates a warning, however. So do the check via the factory instead. !>
-bool <if (r.factory.g.lexer)><lexer.name><else><parser.name><endif>::<r.name>Sempred(<r.ctxType> *_localctx, size_t predicateIndex) {
+bool <if (r.factory.g.lexer)><lexer.name><else><parser.name><endif>::<r.name>Sempred([[maybe_unused]] <r.ctxType> *_localctx, size_t predicateIndex) {
   switch (predicateIndex) {
     <actions: {index | case <index>: return <actions.(index)>}; separator=";\n">;