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regex: treat \| in BRE as alternation 

The standard does not define semantics for \| in BRE, but some code
depends on it meaning alternation. Empty alternative expression is
allowed to be consistent with ERE.

Based on a patch by Rob Landley.
This commit is contained in:
Szabolcs Nagy 2015-04-18 16:47:17 +00:00 committed by Rich Felker
parent 7eaa76fc2e
commit da4cc13b97
1 changed files with 17 additions and 2 deletions
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19
src/regex/regcomp.c
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@ -841,6 +841,14 @@ static reg_errcode_t parse_atom(tre_parse_ctx_t *ctx, const char *s)
/* reject repetitions after empty expression in BRE */
if (!ere)
return REG_BADRPT;
case '|':
/* extension: treat \| as alternation in BRE */
if (!ere) {
node = tre_ast_new_literal(ctx->mem, EMPTY, -1, -1);
s--;
goto end;
}
/* fallthrough */
default:
if (!ere && (unsigned)*s-'1' < 9) {
/* back reference */
@ -918,6 +926,7 @@ parse_literal:
s += len;
break;
}
end:
if (!node)
return REG_ESPACE;
ctx->n = node;
@ -1016,13 +1025,20 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
if ((ere && *s == '|') ||
(ere && *s == ')' && depth) ||
(!ere && *s == '\\' && s[1] == ')') ||
/* extension: treat \| as alternation in BRE */
(!ere && *s == '\\' && s[1] == '|') ||
!*s) {
/* extension: empty branch is unspecified (), (|a), (a|)
here they are not rejected but match on empty string */
int c = *s;
nunion = tre_ast_new_union(ctx->mem, nunion, nbranch);
nbranch = 0;
if (c != '|') {
if (c == '\\' && s[1] == '|') {
s+=2;
} else if (c == '|') {
s++;
} else {
if (c == '\\') {
if (!depth) return REG_EPAREN;
s+=2;
@ -1042,7 +1058,6 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
nunion = tre_stack_pop_voidptr(stack);
goto parse_iter;
}
s++;
}
}
}