Q39239: "Expression Too Complex", "Stack Overflow", Adding Strings

Article: Q39239
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b buglist4.50 B_BasicCom | mspl13_basic
Last Modified: 20-SEP-1990

When the program below concatenates more than 19 string variables
together in one equation, the BC.EXE compiler can give a misleading
error message at compile time.

Microsoft has confirmed this to be a problem in Microsoft QuickBASIC
versions 4.00, 4.00b, and 4.50 for MS-DOS; in Microsoft BASIC Compiler
versions 6.00 and 6.00b (buglist6.00, buglist6.00b) for MS-DOS and MS
OS/2; and in Microsoft BASIC Professional Development System (PDS)
versions 7.00 and 7.10 (buglist7.00, buglist7.10) for MS-DOS and MS
OS/2. We are researching this problem and will post new information
here as it becomes available.

To work around this problem, split up the concatenation line so that
the program does two concatenations on separate lines.

In QuickBASIC versions 4.00 and 4.50 and BASIC PDS 7.00, BC.EXE gives
the following correct error message, but the message misleadingly
points to the bottom of the next structure (IF..ENDIF, WHILE..WEND,
or SELECT CASE) in the source file after the concatenation:

   Expression Too Complex

BC.EXE should point to the concatenation instead of to the end of the
structure.

In QuickBASIC version 4.00b and Microsoft BASIC Compiler versions 6.00
and 6.00b for MS-DOS and OS/2, BC.EXE displays the following error
message in a continuous stream; you must press CTRL+C or CTRL+BREAK to
stop the compiler:

   run-time error R6000 - stack overflow

The following program will cause problems:

   REM The line continuation character (_) is for display purposes
   REM only and should be removed when typing in the program.
   WHILE a$ = ""
   b$ = INKEY$
   a$ = b$ + c$ + d$ + e$ + f$ + g$ + h$ + i$ + j$ + k$ + l$ _
           + m$ + n$ + o$ + p$ + q$ + r$ + s$ + t$ + u$
   WEND

The program can be changed as follows to correct the problem:

   WHILE a$ = ""
   b$ = INKEY$
   a$ = b$ + c$ + d$ + e$ + f$ + g$ + h$ + i$ + j$ + k$ + l$
   a$ = a$ + m$ + n$ + o$ + p$ + q$ + r$ + s$ + t$ + u$
   WEND

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