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Q68385: PRB: Compiler Lacks Warnings for Options Incompatible with /u

Article: Q68385
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5,1.51,1.52,2.0,2.1,4.0,5.0
Operating System(s): 
Keyword(s): kbCompiler kbVC100 kbVC150 kbVC151 kbVC152 kbVC200 kbVC210 kbVC400 kbVC500
Last Modified: 29-NOV-2001

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The information in this article applies to:

- Microsoft C for MS-DOS 
- Microsoft C/C++ for MS-DOS 
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5, 1.51, 1.52 
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0, 5.0 
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SYMPTOMS
========

In the Microsoft C/C++ compiler, the /u compiler option turns off the definition
of all predefined identifiers. Therefore, other compiler options that implicitly
define identifiers are incompatible with /u. Nevertheless, no warnings or errors
are generated if an option incompatible with /u is specified.

For example, the /J option changes the default char type from signed char to
unsigned char and implicitly defines the macro _CHAR_UNSIGNED. If both /u and /J
are specified on the same command line, the default char type for that
translation unit will be unsigned char but _CHAR_UNSIGNED will not be defined.
Moreover, the compiler issues no warning, not even at warning level 4, that /u
will undefine those macros defined by /J.

CAUSE
=====

This is expected behavior. The /U (undefine) option turns off the definition of
an single identifier already defined for the preprocessor. The /u option turns
off every defined identifier. Both the /U and /u options apply to predefined
names and user defined ones.

Additional query words: 8.00 8.00c 9.00 9.10

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Keywords          : kbCompiler kbVC100 kbVC150 kbVC151 kbVC152 kbVC200 kbVC210 kbVC400 kbVC500 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbZNotKeyword8 kbvc150 kbvc100 kbCCompSearch kbZNotKeyword3 kbVC500 kbVC151 kbVC200 kbVC210 kbVC32bitSearch kbVC16bitSearch kbVC152 kbVC500Search
Version           : :1.0,1.5,1.51,1.52,2.0,2.1,4.0,5.0
Issue type        : kbprb

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