On 2/18/18 11:50 PM, Harald van Dijk wrote:
On 2/14/18 11:50 PM, Harald van Dijk wrote:
On 2/14/18 10:44 PM, Harald van Dijk wrote:
On 2/14/18 9:03 PM, Harald van Dijk wrote:
On 13/02/2018 14:53, Denys Vlasenko wrote:
$ >'\zzzz'
$ >'\wwww'
$ dash -c 'echo "\*"'
\wwww \zzzz

[...]

Currently:

$ dash -c 'foo=a; echo "<${foo#[a\]]}>"'
<>

This is what I expect, and also what bash, ksh and posh do.

With your patch:

$ dash -c 'foo=a; echo "<${foo#[a\]]}>"'
<a>

Does the attached look right as an alternative? It treats a quoted backslash the same way as if it were preceded by CTLESC in _rmescapes. It passes your test case and mine, but I'll do more extensive testing.

It causes preglob's string to potentially grow larger than the original. When called with RMESCAPE_ALLOC, that can be handled by increasing the buffer size, but preglob also gets called without RMESCAPE_ALLOC to modify a string in-place. That's never going to work with this approach. Back to the drawing board...

There is a way to make it work: ensure sufficient memory is always available. Instead of inserting CTLESC, which caused problems, CTLQUOTEMARK+CTLQUOTEMARK can be inserted instead. It's effectively a no-op here.

It required one obvious additional trivial change to the CHECKSTRSPACE invocation, but with that added, the attached passed all testing I could think of. Does this look okay to include, did I miss something, or is there perhaps a better alternative?

Cheers,
Harald van Dijk
diff --git a/src/expand.c b/src/expand.c
index 2a50830..af88a69 100644
--- a/src/expand.c
+++ b/src/expand.c
@@ -1686,12 +1686,17 @@ _rmescapes(char *str, int flag)
 		}
 		if (*p == (char)CTLESC) {
 			p++;
-			if (notescaped)
-				*q++ = '\\';
-		} else if (*p == '\\' && !inquotes) {
-			/* naked back slash */
-			notescaped = 0;
-			goto copy;
+			goto escape;
+		} else if (*p == '\\') {
+			if (inquotes) {
+escape:
+				if (notescaped)
+					*q++ = '\\';
+			} else {
+				/* naked back slash */
+				notescaped = 0;
+				goto copy;
+			}
 		}
 		notescaped = globbing;
 copy:
diff --git a/src/parser.c b/src/parser.c
index 382658e..a847b2e 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -909,7 +909,7 @@ readtoken1(int firstc, char const *syntax, char *eofmark, int striptabs)
 #endif
 		CHECKEND();	/* set c to PEOF if at end of here document */
 		for (;;) {	/* until end of line or end of word */
-			CHECKSTRSPACE(4, out);	/* permit 4 calls to USTPUTC */
+			CHECKSTRSPACE(5, out);	/* permit 5 calls to USTPUTC */
 			switch(syntax[c]) {
 			case CNL:	/* '\n' */
 				if (syntax == BASESYNTAX)
@@ -944,6 +944,9 @@ readtoken1(int firstc, char const *syntax, char *eofmark, int striptabs)
 							eofmark != NULL
 						)
 					) {
+						/* Reserve extra memory in case this backslash will require later escaping. */
+						USTPUTC(CTLQUOTEMARK, out);
+						USTPUTC(CTLQUOTEMARK, out);
 						USTPUTC('\\', out);
 					}
 					USTPUTC(CTLESC, out);

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