Q48186: Compiling Incorrect or Incomplete C Syntax Can Hang Computer

Article: Q48186
Product(s): See article
Version(s): 2.00 2.01
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist2.00 buglist2.01 | mspl13_c
Last Modified: 6-NOV-1989

QuickC Versions 2.00 and 2.01 hang the computer when given certain
unusual and obscure configurations of invalid C syntax.

For example, compiling the code shown below causes QuickC to hang. The
code can be compiled both inside and outside of the environment with
various switches turned on/off, and a hang results.

To work around the problem, correct the invalid or incomplete syntax.
If you are unsure of the location of the syntax errors, then use the
QCL command-line compiler to locate the lines containing the specified
errors.

Make note of these error messages and then reboot your machine. You
should correct these particular syntax errors.

Note: This particular behavior of QuickC occurs only with very unusual
and invalid C syntax.

Microsoft has confirmed this to be a problem with QuickC Version 2.00
and 2.01. We are researching this problem and will post new
information as it becomes available.

The following example demonstrates the problem. To correct this
problem, place _dos_findfirst within a function, and correct the
existing function definitions.

The source code for prg.c is as follows:

_dos_findfirst

void wrflen(value)
long value;
{
     int buffer;

     buffer = value;

     for (;;) {
     }
}

int wrvlen(value)
long value;
{
     int buffer;

     while (1) {
     }
}

The QCL outputs the following text before hanging:

Microsoft (R) Quick C Compiler Version 2.00
Copyright (C) Microsoft Corp 1987-1989.  All rights reserved.

prg.c (3) error C2054: expected '(' to follow '_dos_findfirst'
prg.c (4) error C2085: 'wrflen': not in formal parameter list
prg.c (4) error C2144: syntax error: missing ';' before type 'long'
prg.c (8) error C2065: 'value': undefined

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