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Add explicit non-capturing groups.
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This is useful in POSIX mode (with --posix-captures option) in order to
avoid unnecessary captures and reduce the amount of tags.

The new syntax for non-capturing groups is `(? ...)`.

Add tests for the new feature. Note that test results coincide with the
corresponding test for implicit groups (where the same group is not
parenthesized at all, but implicit grouping is achieved with the help
of a named definition).

This addresses bugs #438 "POSIX captures processing" and #308
"Overloading precedence marker (e.g. (pattern)) with 'posix' group
markers (also parenthesis) causes loss of full functionality".
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@skvadrik
skvadrik committed Mar 24, 2023
1 parent f519385 commit 1edd25d
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Showing 8 changed files with 1,067 additions and 70 deletions.
146 changes: 77 additions & 69 deletions bootstrap/src/parse/parser.cc
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3 changes: 2 additions & 1 deletion src/parse/parser.ypp
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Expand Up @@ -218,7 +218,8 @@ primary
$$ = ast.ref($$, $1);
}
}
| '(' expr ')' { $$ = ast.cap($2); }
| '(' expr ')' { $$ = ast.cap($2); } // capturing group (in POSIX mode)
| '(' '?' expr ')' { $$ = ast.ref($3, "<group>"); } // non-capturing group
;

%%
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273 changes: 273 additions & 0 deletions test/posix_captures/non_capturing_explicit_2.c
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@@ -0,0 +1,273 @@
/* Generated by re2c */
// re2c $INPUT -o $OUTPUT -i --posix-captures


{
YYCTYPE yych;
if ((YYLIMIT - YYCURSOR) < 2) YYFILL(2);
yych = *YYCURSOR;
switch (yych) {
case 'a': goto yy3;
default: goto yy1;
}
yy1:
++YYCURSOR;
yy2:
{}
yy3:
yych = *++YYCURSOR;
switch (yych) {
case 'a': goto yy4;
default: goto yy2;
}
yy4:
++YYCURSOR;
yynmatch = 1;
yypmatch[0] = YYCURSOR - 2;
yypmatch[1] = YYCURSOR;
{}
}



{
YYCTYPE yych;
if ((YYLIMIT - YYCURSOR) < 4) YYFILL(4);
yych = *YYCURSOR;
switch (yych) {
case 'a': goto yy8;
default: goto yy6;
}
yy6:
++YYCURSOR;
yy7:
{}
yy8:
yych = *(YYMARKER = ++YYCURSOR);
switch (yych) {
case 'b': goto yy9;
default: goto yy7;
}
yy9:
yych = *++YYCURSOR;
switch (yych) {
case 'a': goto yy11;
default: goto yy10;
}
yy10:
YYCURSOR = YYMARKER;
goto yy7;
yy11:
yych = *++YYCURSOR;
switch (yych) {
case 'b': goto yy12;
default: goto yy10;
}
yy12:
++YYCURSOR;
yynmatch = 1;
yypmatch[0] = YYCURSOR - 4;
yypmatch[1] = YYCURSOR;
{}
}



{
YYCTYPE yych;
if ((YYLIMIT - YYCURSOR) < 4) YYFILL(4);
yych = *YYCURSOR;
switch (yych) {
case 'a': goto yy16;
default: goto yy14;
}
yy14:
++YYCURSOR;
yy15:
{}
yy16:
yych = *(YYMARKER = ++YYCURSOR);
switch (yych) {
case 'b': goto yy17;
default: goto yy15;
}
yy17:
yych = *++YYCURSOR;
switch (yych) {
case 'a': goto yy19;
default: goto yy18;
}
yy18:
YYCURSOR = YYMARKER;
goto yy15;
yy19:
yych = *++YYCURSOR;
switch (yych) {
case 'b': goto yy20;
default: goto yy18;
}
yy20:
++YYCURSOR;
yynmatch = 3;
yypmatch[0] = YYCURSOR - 4;
yypmatch[1] = YYCURSOR;
yypmatch[2] = YYCURSOR - 3;
yypmatch[3] = YYCURSOR - 2;
yypmatch[4] = YYCURSOR - 1;
yypmatch[5] = YYCURSOR;
{}
}



{
YYCTYPE yych;
if ((YYLIMIT - YYCURSOR) < 2) YYFILL(2);
yych = *YYCURSOR;
switch (yych) {
case 'a':
case 'b': goto yy24;
default: goto yy22;
}
yy22:
++YYCURSOR;
yy23:
{}
yy24:
yych = *++YYCURSOR;
switch (yych) {
case 'a':
case 'b': goto yy25;
default: goto yy23;
}
yy25:
++YYCURSOR;
yynmatch = 1;
yypmatch[0] = YYCURSOR - 2;
yypmatch[1] = YYCURSOR;
{}
}



{
YYCTYPE yych;
if ((YYLIMIT - YYCURSOR) < 2) YYFILL(2);
yych = *YYCURSOR;
switch (yych) {
case 'a': goto yy29;
case 'b': goto yy30;
default: goto yy27;
}
yy27:
++YYCURSOR;
yy28:
{}
yy29:
yych = *++YYCURSOR;
switch (yych) {
case 'a':
yyt1 = NULL;
goto yy31;
case 'b':
yyt1 = NULL;
goto yy33;
default: goto yy28;
}
yy30:
yych = *++YYCURSOR;
switch (yych) {
case 'a':
yyt1 = YYCURSOR;
goto yy31;
case 'b':
yyt1 = YYCURSOR;
goto yy33;
default: goto yy28;
}
yy31:
++YYCURSOR;
yyt2 = NULL;
yy32:
yynmatch = 3;
yypmatch[3] = yyt1;
yypmatch[5] = yyt2;
yypmatch[0] = YYCURSOR - 2;
yypmatch[1] = YYCURSOR;
yypmatch[2] = yyt1;
if (yyt1 != NULL) yypmatch[2] -= 1;
yypmatch[4] = yyt2;
if (yyt2 != NULL) yypmatch[4] -= 1;
{}
yy33:
++YYCURSOR;
yyt2 = YYCURSOR;
goto yy32;
}



{
YYCTYPE yych;
if (YYLIMIT <= YYCURSOR) YYFILL(1);
yych = *YYCURSOR;
yyt1 = YYCURSOR;
switch (yych) {
case 'a': goto yy36;
default: goto yy35;
}
yy35:
yynmatch = 1;
yypmatch[0] = yyt1;
yypmatch[1] = YYCURSOR;
{}
yy36:
++YYCURSOR;
if (YYLIMIT <= YYCURSOR) YYFILL(1);
yych = *YYCURSOR;
switch (yych) {
case 'a': goto yy36;
default: goto yy35;
}
}



{
YYCTYPE yych;
if (YYLIMIT <= YYCURSOR) YYFILL(1);
yych = *YYCURSOR;
switch (yych) {
case 'a':
yyt1 = YYCURSOR;
goto yy39;
default:
yyt2 = NULL;
yyt1 = YYCURSOR;
goto yy38;
}
yy38:
yynmatch = 3;
yypmatch[0] = yyt1;
yypmatch[3] = yyt2;
yypmatch[5] = yyt2;
yypmatch[1] = YYCURSOR;
yypmatch[2] = yyt2;
if (yyt2 != NULL) yypmatch[2] -= 2;
yypmatch[4] = yyt2;
if (yyt2 != NULL) yypmatch[4] -= 2;
{}
yy39:
++YYCURSOR;
if (YYLIMIT <= YYCURSOR) YYFILL(1);
yych = *YYCURSOR;
switch (yych) {
case 'a': goto yy39;
default:
yyt2 = NULL;
goto yy38;
}
}

posix_captures/non_capturing_explicit_2.re:35:9: warning: rule matches empty string [-Wmatch-empty-string]
posix_captures/non_capturing_explicit_2.re:40:9: warning: rule matches empty string [-Wmatch-empty-string]
41 changes: 41 additions & 0 deletions test/posix_captures/non_capturing_explicit_2.re
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@@ -0,0 +1,41 @@
// re2c $INPUT -o $OUTPUT -i --posix-captures

/*!local:re2c
x = (?"a");
x x {}
* {}
*/

/*!local:re2c
x = (?"a" "b");
x x {}
* {}
*/

/*!local:re2c
x = (?"a" ("b"));
x x {}
* {}
*/

/*!local:re2c
x = (?"a" | "b");
x x {}
* {}
*/

/*!local:re2c
x = (?"a" | ("b"));
x x {}
* {}
*/

/*!local:re2c
x = (?"a" | "aa");
x*x* {}
*/

/*!local:re2c
x = (?"a" | ("aa"));
x*x* {}
*/

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