Subject: Re: I: gcc ... -U_WIN32 ... may cause problems
From: [email-masked] (Larry Hall RFK Partners Inc)

5 Sep 1998 07:10:28 -0700
Message-ID: <[email-masked]>
References: <[email-masked]>
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To: Mumit Khan <[email-masked]>
Cc: [email-masked]

At 03:23 PM 9/2/98 -0500, Mumit Khan wrote:
>"Larry Hall (RFK Partners Inc)" <[email-masked]> writes:
>> The best argument I have for getting rid of _WIN32 from cygwin and mingw is 
>> that MS docs claim _WIN32 is MS compiler specific.  
>
>As far as I know, _MSC_VER, not _WIN32, is the microsoft-compiler specific 
>macro. A quick look at some of the microsoft's headers, eg., pshpack1.h,
>suggests the same as well. My *rather old* on-line API docs here tell me 
>that _WIN32 is specific to Microsoft Windows Operating System. Please cite 
>the docs you mentiond so I can verify.
>

Below is documentation that comes with VC++ 5.0.  See table 1.2 for 
Microsoft specific predefined macros.

--------------------------------------------------------------------------

Predefined Macros

The compiler recognizes six predefined ANSI C macros (see Table 1.1), and the Microsoft C++ implementation provides several more (see Table 1.2). These macros take no arguments and cannot be redefined. Their value (except for __LINE__ and __FILE__) must be constant throughout compilation. Some of the predefined macros listed below are defined with multiple values. Their values can be set by selecting the corresponding menu option in Microsoft Developer Studio, or by using a command-line switch. See the tables below for more information.

Table 1.1 ANSI Predefined Macros

Macro

Description

__DATE__

The compilation date of the current source file. The date is a string literal of the form Mmm dd yyyy. The month name Mmm is the same as for dates generated by the library function asctime declared in TIME.H. 

__FILE__

The name of the current source file. __FILE__ expands to a string surrounded by double quotation marks. 

__LINE__

The line number in the current source file. The line number is a decimal integer constant. It can be altered with a #line directive. 

__STDC__

Indicates full conformance with the ANSI C standard. Defined as the integer constant 1 only if the /Za compiler option is given and you are not compiling C++ code; otherwise is undefined. 

__TIME__

The most recent compilation time of the current source file. The time is a string literal of the form hh:mm:ss. 

__TIMESTAMP__

The date and time of the last modification of the current source file, expressed as a string literal in the form Ddd Mmm Date hh:mm:ss yyyy, where Ddd is the abbreviated day of the week and Date is an integer from 1 to 31.

Table 1.2 Microsoft-Specific Predefined Macros 

Macro

Description

_CHAR_UNSIGNED

Default char type is unsigned. Defined when /J is specified. 

__cplusplus

Defined for C++ programs only.

_CPPRTTI

Defined for code compiled with /GR (Enable Run-Time Type Information).

_CPPUNWIND

Defined for code compiled with /GX (Enable Exception Handling).

_DLL

Defined when /MD or /MDd (Multithread DLL) is specified.

_M_ALPHA

Defined for DEC ALPHA platforms. It is defined as 1 by the ALPHA compiler, and it is not defined if another compiler is used.

_M_IX86

Defined for x86 processors. See Table 1.3 for more details.

_M_MPPC

Defined for Power Macintosh platforms. Default is 601 (/QP601). See Table 1.4 for more details.

_M_MRX000

Defined for MIPS platforms. Default is 4000 (/QMR4000). See Table 1.5 for more details.

_M_PPC

Defined for PowerPC platforms. Default is 604 (/QP604). See Table 1.6 for more details.

_MFC_VER

Defines the MFC version. Defined as 0x0421 for Microsoft Foundation Class Library 4.21. Always defined.

_MSC_VER

Defines the compiler version. Defined as 1100 for Microsoft Visual C++™ 5.0. Always defined.

_MT

Defined when /MD or /MDd (Multithreaded DLL) or /MT or /MTd (Multithreaded) is specified. 

_WIN32

Defined for applications for Win32®. Always defined. 

As shown in following tables, the compiler generates a value for the preprocessor identifiers that reflect the processor option specified.

Table 1.3 Values for _M_IX86

Option in Developer Studio

Command-Line Option

Resulting Value

Blend

/GB

_M_IX86 = 500 (Default. Future compilers will emit a different value to reflect the dominant processor.)

Pentium

/G5

_M_IX86 = 500

Pentium Pro

/G6

_M_IX86 = 600

80386

/G3

_M_IX86 = 300

80486

/G4

_M_IX86 = 400

Table 1.4 Values for _M_MPPC

Option in development environment

Command-Line Option

Resulting Value

PowerPC 601

/QP601

_M_MPPC = 601 (Default)

PowerPC 603

/QP603

_M_MPPC = 603

PowerPC 604

/QP604

_M_MPPC = 604

PowerPC 620

/QP620

_M_MPPC = 620

Table 1.5 Values for _M_MRX000

Option in Developer Studio

Command-Line Option

Resulting Value

R4000

/QMR4000

_M_MRX000 = 4000 (Default)

R4100

/QMR4100

_M_MRX000 = 4100

R4200

/QMR4200

_M_MRX000 = 4200

R4400

/QMR4400

_M_MRX000 = 4400

R4600

/QMR4600

_M_MRX000 = 4600

R10000

/QMR10000

_M_MRX000 = 10000

Table 1.6 Values for _M_PPC

Option in Developer Studio

Command-Line Option

Resulting Value

PowerPC 601

/QP601

_M_PPC = 601

PowerPC 603

/QP603

_M_PPC = 603

PowerPC 604

/QP604

_M_PPC = 604 (Default)

PowerPC 620

/QP620

_M_PPC = 620
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