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handle ^ and $ in BRE subexpression start and end as anchors

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In BRE, ^ is an anchor at the beginning of an expression, optionally
it may be an anchor at the beginning of a subexpression and must be
treated as a literal otherwise.

Previously musl treated ^ in subexpressions as literal, but at least
glibc and gnu sed treats it as an anchor and that's the more useful
behaviour: it can always be escaped to get back the literal meaning.

Same for $ at the end of a subexpression.

Portable BRE should not rely on this, but there are sed commands in
build scripts which do.

This changes the meaning of the BREs:

	\(^a\)
	\(a\|^b\)
	\(a$\)
	\(a$\|b\)
This commit is contained in:
Szabolcs Nagy
2016-12-16 23:26:29 -05:00
committed by Rich Felker
parent adfe682eb0
commit 7a4c25d780
1 changed files with 12 additions and 9 deletions
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src/regex/regcomp.c
+12 -9
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@@ -401,8 +401,8 @@ typedef struct {
tre_ast_node_t *n;
/* Position in the regexp pattern after a parse function returns. */
const char *s;
/* The first character of the regexp. */
const char *re;
/* The first character of the last subexpression parsed. */
const char *start;
/* Current submatch ID. */
int submatch_id;
/* Current position (number of literal). */
@@ -876,14 +876,14 @@ static reg_errcode_t parse_atom(tre_parse_ctx_t *ctx, const char *s)
break;
case '^':
/* '^' has a special meaning everywhere in EREs, and at beginning of BRE. */
if (!ere && s != ctx->re)
if (!ere && s != ctx->start)
goto parse_literal;
node = tre_ast_new_literal(ctx->mem, ASSERTION, ASSERT_AT_BOL, -1);
s++;
break;
case '$':
/* '$' is special everywhere in EREs, and in the end of the string in BREs. */
if (!ere && s[1])
/* '$' is special everywhere in EREs, and at the end of a BRE subexpression. */
if (!ere && s[1] && (s[1]!='\\'|| (s[2]!=')' && s[2]!='|')))
goto parse_literal;
node = tre_ast_new_literal(ctx->mem, ASSERTION, ASSERT_AT_EOL, -1);
s++;
@@ -944,7 +944,7 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
{
tre_ast_node_t *nbranch=0, *nunion=0;
int ere = ctx->cflags & REG_EXTENDED;
const char *s = ctx->re;
const char *s = ctx->start;
int subid = 0;
int depth = 0;
reg_errcode_t err;
@@ -962,6 +962,7 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
s++;
depth++;
nbranch = nunion = 0;
ctx->start = s;
continue;
}
if ((!ere && *s == '\\' && s[1] == ')') ||
@@ -994,8 +995,8 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
if (*s=='\\')
s++;
/* handle ^* at the start of a complete BRE. */
if (!ere && s==ctx->re+1 && s[-1]=='^')
/* handle ^* at the start of a BRE. */
if (!ere && s==ctx->start+1 && s[-1]=='^')
break;
/* extension: multiple consecutive *+?{,} is unspecified,
@@ -1038,8 +1039,10 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
if (c == '\\' && s[1] == '|') {
s+=2;
ctx->start = s;
} else if (c == '|') {
s++;
ctx->start = s;
} else {
if (c == '\\') {
if (!depth) return REG_EPAREN;
@@ -2705,7 +2708,7 @@ regcomp(regex_t *restrict preg, const char *restrict regex, int cflags)
memset(&parse_ctx, 0, sizeof(parse_ctx));
parse_ctx.mem = mem;
parse_ctx.stack = stack;
parse_ctx.re = regex;
parse_ctx.start = regex;
parse_ctx.cflags = cflags;
parse_ctx.max_backref = -1;
errcode = tre_parse(&parse_ctx);