The #pragma preprocessor directives C program example

 

Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows XP Pro SP2

Header file: Standard

Additional library: none/default

Additional project setting: Set project to be compiled as C

Project -> your_project_name Properties -> Configuration Properties -> C/C++ -> Advanced -> Compiled As: Compiled as C Code (/TC)

Other info: none

To do: Printing date, time, version and file name using the #pragma message preprocessor directives

To show: How to use the C/C++ #pragma message preprocessor directive

 

The #pragma directives offer a way for each compiler to offer machine- and operating system-specific features while retaining overall compatibility with the C and C++ languages. Pragmas are machine- or operating system-specific by definition, and are usually different for every compiler. A typical use of the message pragma is to display informational messages at compile time

 

 

// The #pragma directives

#include <stdio.h>

#include <stdlib.h>

 

// displays either "You are compiling using version xxx of BC++" (where xxx is the version number)

// or "This compiler is not Borland C++", date, time console or not... by using several related predefined macro such as __DATE__ etc

#ifdef __BORLANDC__

#pragma message You are compiling using Borland C++ version __BORLANDC__.

#else

#pragma message("")

#pragma message ("This compiler is not Borland C++")

#endif

#pragma message ("Time:" __TIME__)

#pragma message ("Date:" __DATE__)

#pragma message( "Compiling: " __FILE__ )

#pragma message( "Last modified on: " __TIMESTAMP__ )

#pragma message("")

 

int main(void)

{

return 0;

}

 

Output example:

 

// No output

 

You can see the following statements in the output window after the compilation.

 

1>------ Build started: Project: myaddr, Configuration: Debug Win32 ------

1>Compiling...

1>myaddr.cpp

1>This compiler is not Borland C++

1>Time:19:44:20

1>Date:Nov 16 2006

1>Compiling: f:\vc2005project\myaddr\myaddr\myaddr.cpp

1>Last modified on: Thu Nov 16 18:45:37 2006

1>Build log was saved at "file://f:\vc2005project\myaddr\myaddr\Debug\BuildLog.htm"

1>myaddr - 0 error(s), 0 warning(s)

========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

 

 

The Microsoft C and C++ compilers recognize the following pragmas:

 

alloc_text - Names the code section where the specified function definitions are to reside. The pragma must occur between a function declarator and the function definition for the named functions.

auto_inline - Excludes any functions defined within the range where off is specified from being considered as candidates for automatic inline expansion.

bss_seg - Specifies the segment where uninitialized variables are stored in the .obj file.

check_stack - Instructs the compiler to turn off stack probes if off (or â€") is specified, or to turn on stack probes if on (or +) is specified.

code_seg - Specifies the segment where functions are stored in the .obj file.

comment - Places a comment record into an object file or executable file.

component - Controls the collecting of browse information or dependency information from within source files.

conform (Supported only by the C++ compiler) - Specifies the run-time behavior of the /Zc:forScope compiler option.

const_seg - Specifies the segment where const variables are stored in the .obj file.

data_seg - Specifies the data segment where initialized variables are stored in the .obj file.

deprecated - The deprecated pragma lets you indicate that a function, type, or any other identifier may no longer be supported in a future release or should no longer be used.

fenv_access - Disables (ON) or enables (OFF) optimizations that could change flag tests and mode changes.

float_control - Specifies floating-point behavior for a function.

fp_contract - Determines whether floating-point contraction will take place.

function - Specifies that calls to functions specified in the pragma's argument list be generated.

hdrstop - Gives you additional control over pre-compilation file names and over the location at which the compilation state is saved.

include_alias - Specifies that short_filename is to be used as an alias for long_filename.

init_seg (Supported only by the C++ compiler) - Specifies a keyword or code section that affects the order in which startup code is executed.

inline_depth - Specifies the inline heuristic search depth, such that, no function will be inlined if it is at a depth (in the call graph) greater than n.

inline_recursion - Controls the inline expansion of direct or mutually recursive function calls.

intrinsic - Specifies that calls to functions specified in the pragma's argument list are intrinsic.

make_public - Indicates that a native type should have public assembly accessibility.

managed - Enable function-level control for compiling functions as managed or unmanaged.

message - Sends a string literal to the standard output without terminating the compilation.

omp - Takes one or more OpenMP directives, along with any optional directive clauses.

once - Specifies that the file will be included (opened) only once by the compiler when compiling a source code file.

optimize - Specifies optimizations to be performed on a function-by-function basis.

pack - Specifies packing alignment for structure, union, and class members.

pointers_to_members (Supported only by the C++ compiler) - Specifies whether a pointer to a class member can be declared before its associated class definition and is used to control the pointer size and the code required to interpret the pointer.

pop_macro - Sets the value of the macro_name macro to the value on the top of the stack for this macro.

push_macro - Saves the value of the macro_name macro on the top of the stack for this macro.

region, endregion - #pragma region lets you specify a block of code that you can expand or collapse when using the outlining feature of the Visual Studio Code Editor.

runtime_checks - Disables or restores the /RTC settings.

section - Creates a section in an .obj file.

setlocale - Defines the locale (Country/Region and language) to be used when translating wide-character constants and string literals.

unmanaged - Enable function-level control for compiling functions as managed or unmanaged.

vtordisp (Supported only by the C++ compiler) - Enables the addition of the hidden vtordisp construction/destruction displacement member.

warning - Allows selective modification of the behavior of compiler warning messages.

 

 

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