34560: Fix $(( that's actually a multiline cmd subst.

ChangeLog

@@ -1,5 +1,7 @@
 2015-02-16  Peter Stephenson  <p.stephenson@samsung.com>
 
+	* 34560: Src/input. Src/lex.c, Src/zsh.h, Test/C01arith.ztst: 
+
 	* 34558: Doc/Zsh/func.yo: preexec doc erroneously claimed $1
 	was empty if line removed from history.
 

Src/input.c

@@ -330,8 +330,37 @@ inputline(void)
 	}
     }
     isfirstch = 1;
+    if ((inbufflags & INP_APPEND) && inbuf) {
+	/*
+	 * We need new input but need to be able to back up
+	 * over the old input, so append this line.
+	 * Pushing the line onto the stack doesn't have the right
+	 * effect.
+	 *
+	 * This is quite a simple and inefficient fix, but currently
+	 * we only need it when backing up over a multi-line $((...
+	 * that turned out to be a command substitution rather than
+	 * a math substitution, which is a very special case.
+	 * So it's not worth rewriting.
+	 */
+	char *oinbuf = inbuf;
+	int newlen = strlen(ingetcline);
+	int oldlen = (int)(inbufptr - inbuf) + inbufleft;
+	if (inbufflags & INP_FREE) {
+	    inbuf = realloc(inbuf, oldlen + newlen + 1);
+	    inbufptr += inbuf - oinbuf;
+	    strcpy(inbuf + oldlen, ingetcline);
+	} else {
+	    /* Paranoia: don't think this is used */
+	    DPUTS(1, "Appending to unallocated input line.");
+	}
+	inbufleft += newlen;
+	inbufct += newlen;
+	inbufflags |= INP_FREE;
+    } else {
 	/* Put this into the input channel. */
 	inputsetline(ingetcline, INP_FREE);
+    }
 
     return 0;
 }

Src/lex.c

@@ -483,9 +483,13 @@ cmd_or_math(int cs_type)
 {
     int oldlen = lexbuf.len;
     int c;
+    int oinflags = inbufflags;
 
     cmdpush(cs_type);
+    inbufflags |= INP_APPEND;
     c = dquote_parse(')', 0);
+    if (!(oinflags & INP_APPEND))
+	inbufflags &= ~INP_APPEND;
     cmdpop();
     *lexbuf.ptr = '\0';
     if (!c) {

Src/zsh.h

@@ -410,6 +410,7 @@ enum {
 #define INP_CONT      (1<<3)	/* continue onto previously stacked input  */
 #define INP_ALCONT    (1<<4)	/* stack is continued from alias expn.     */
 #define INP_LINENO    (1<<5)    /* update line number                      */
+#define INP_APPEND    (1<<6)    /* Append new lines to allow backup        */
 
 /* Flags for metafy */
 #define META_REALLOC	0

Test/C01arith.ztst

@@ -318,3 +318,38 @@
 # 0.75 is exactly representable, don't expect rounding error.
 >0
 >0.75
+
+  # The following tests for a bug that only happens when
+  # backing up over input read a line at a time, so we'll
+  # read the input from stdin.
+  $ZTST_testdir/../Src/zsh -f <<<'
+  print $((echo first command
+  ); echo second command)
+  print third command
+  '
+0:Backing up a line of input when finding out it's not arithmetic
+>first command second command
+>third command
+
+  $ZTST_testdir/../Src/zsh -f <<<'
+  print $((3 +
+  4))
+  print next line
+  '
+0:Not needing to back up a line when reading multiline arithmetic
+>7
+>next line
+
+  $ZTST_testdir/../Src/zsh -f <<<'
+  print $((case foo in
+  bar)
+  echo not this no, no
+  ;;
+  foo)
+  echo yes, this one
+  ;;
+  esac)
+  print after case in subshell)
+  '
+0:Non-arithmetic subst with command subsitution parse from hell
+>yes, this one after case in subshell