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2ca39ffd4

Denys Vlasenko

2023-06-08

SUCCESS Duration: 156s

Subject

awk: fix subst code to handle "start of word" pattern correctly (needs REG_STARTEND)

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

editors/awk.c +36 -13 testsuite/awk.tests +15 -13

editors/awk.c+36 -13

@@ -2504,17 +2504,46 @@ static int awk_sub(node rn, const char repl, int nm, var src, var dest /*,in
	regex_t sreg, *regex;
	/* True only if called to implement gensub(): */
	int subexp = (src != dest);
-
+	#if defined(REG_STARTEND)
+	const char *src_string;
+	size_t src_strlen;
+	regexec_flags = REG_STARTEND;
+	#else
+	regexec_flags = 0;
+	#endif
	resbuf = NULL;
	residx = 0;
	match_no = 0;
-	regexec_flags = 0;
	regex = as_regex(rn, &sreg);
	sp = getvar_s(src ? src : intvar[F0]);
+	#if defined(REG_STARTEND)
+	src_string = sp;
+	src_strlen = strlen(src_string);
+	#endif
	replen = strlen(repl);
-	while (regexec(regex, sp, 10, pmatch, regexec_flags) == 0) {
-	int so = pmatch[0].rm_so;
-	int eo = pmatch[0].rm_eo;
+	for (;;) {
+	int so, eo;
+
+	#if defined(REG_STARTEND)
+	// REG_STARTEND: "This flag is a BSD extension, not present in POSIX"
+	size_t start_ofs = sp - src_string;
+	pmatch[0].rm_so = start_ofs;
+	pmatch[0].rm_eo = src_strlen;
+	if (regexec(regex, src_string, 10, pmatch, regexec_flags) != 0)
+	break;
+	eo = pmatch[0].rm_eo - start_ofs;
+	so = pmatch[0].rm_so - start_ofs;
+	#else
+	// BUG:
+	// gsub(/\<b*/,"") on "abc" matches empty string at "a...",
+	// advances sp one char (see "Empty match" comment later) to "bc"
+	// ... and erroneously matches "b" even though it is NOT at the word start.
+	enum { start_ofs = 0 };
+	if (regexec(regex, sp, 10, pmatch, regexec_flags) != 0)
+	break;
+	so = pmatch[0].rm_so;
+	eo = pmatch[0].rm_eo;
+	#endif

	//bb_error_msg("match %u: [%u,%u] '%s'%p", match_no+1, so, eo, sp,sp);
	resbuf = qrealloc(resbuf, residx + eo + replen, &resbufsize);
@@ -2543,7 +2572,7 @@ static int awk_sub(node rn, const char repl, int nm, var src, var dest /*,in
	}
	n = pmatch[j].rm_eo - pmatch[j].rm_so;
	resbuf = qrealloc(resbuf, residx + replen + n, &resbufsize);
-	memcpy(resbuf + residx, sp + pmatch[j].rm_so, n);
+	memcpy(resbuf + residx, sp + pmatch[j].rm_so - start_ofs, n);
	residx += n;
	} else
	resbuf[residx++] = c;
@@ -2557,12 +2586,6 @@ static int awk_sub(node rn, const char repl, int nm, var src, var dest /*,in
	if (eo == so) {
	/* Empty match (e.g. "b*" will match anywhere).
	* Advance by one char. */
-	//BUG (bug 1333):
-	//gsub(/\<b*/,"") on "abc" will reach this point, advance to "bc"
-	//... and will erroneously match "b" even though it is NOT at the word start.
-	//we need REG_NOTBOW but it does not exist...
-	//TODO: if EXTRA_COMPAT=y, use GNU matching and re_search,
-	//it should be able to do it correctly.
	/* Subtle: this is safe only because
	* qrealloc allocated at least one extra byte */
	resbuf[residx] = *sp;
@@ -2571,7 +2594,7 @@ static int awk_sub(node rn, const char repl, int nm, var src, var dest /*,in
	sp++;
	residx++;
	}
-	regexec_flags = REG_NOTBOL;
+	regexec_flags \|= REG_NOTBOL;
	}

	resbuf = qrealloc(resbuf, residx + strlen(sp), &resbufsize);

testsuite/awk.tests+15 -13

@@ -557,14 +557,12 @@ testing 'awk gensub backslashes \' \
	'awk '$sq'BEGIN { s="\\"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\
	\\\|\\
-	' \
-	'' ''
+	' '' ''
	testing 'awk gensub backslashes \\' \
	'awk '$sq'BEGIN { s="\\\\"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\\\
	\\\|\\
-	' \
-	'' ''
+	' '' ''
	# gawk 5.1.1 handles trailing unpaired \ inconsistently.
	# If replace string is single \, it is used verbatim,
	# but if it is \\\ (three slashes), gawk uses "\<NUL>" (!!!), not "\\" as you would expect.
@@ -572,31 +570,35 @@ testing 'awk gensub backslashes \\\' \
	'awk '$sq'BEGIN { s="\\\\\\"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\\\\\
	\\\\\|\\\\
-	' \
-	'' ''
+	' '' ''
	testing 'awk gensub backslashes \\\\' \
	'awk '$sq'BEGIN { s="\\\\\\\\"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\\\\\\\
	\\\\\|\\\\
-	' \
-	'' ''
+	' '' ''
	testing 'awk gensub backslashes \&' \
	'awk '$sq'BEGIN { s="\\&"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\&
	&\|&
-	' \
-	'' ''
+	' '' ''
	testing 'awk gensub backslashes \0' \
	'awk '$sq'BEGIN { s="\\0"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\0
	a\|a
-	' \
-	'' ''
+	' '' ''
	testing 'awk gensub backslashes \\0' \
	'awk '$sq'BEGIN { s="\\\\0"; print "s=" s; print gensub("a", s, "g", "a\|a") }'$sq \
	's=\\\\0
	\\0\|\\0
-	' \
+	' '' ''
+
+	# The "b" in "abc" should not match <b* pattern.
+	# Currently we use REG_STARTEND ("This flag is a BSD extension, not present in POSIX")
+	# to implement the code to handle this correctly, but if your libc has no REG_STARTEND,
+	# the alternative code mishandles this case.
+	testing 'awk gsub erroneous word start match' \
+	"awk 'BEGIN { a=\"abc\"; gsub(/\<b*/,\"\",a); print a }'" \
+	'abc\n' \
	'' ''

	exit $FAILCOUNT