December 27th, , AM 7. Thanks to all, I only want to get if the macro is hard defined. Thanks again, bow December 27th, , AM 8. If it is to be compiled as straight "C" it is not defined.
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Copyright TechnologyAdvice. CodeGuru Home. This is because of the included headers. And in our example, we have included just one header. The translation unit becomes bigger and bigger as we keep including headers. This preprocess and compile process is similar for C language.
It follows the C rules for compiling, and the way it includes header files and produces object code is nearly the same. Compile it or run make and all the steps to create the two example apps to be executed to create the sum. No symbols are imported and two symbols are exported: sumF and sumI.
Those symbols are exported as part of the. The standard way to do it is to create a header file that declares them and includes them in whatever source file we want to call them. The header can have any name and extension. I chose sum. If I include this header from a C source file, I want it to become:. There are two functions that were declared with C linkage in print. I had to differentiate them from each other by postfixing an Int or a Float to the end of their names.
This can be seen in the nm output of print. Those undefined symbols are supposed to be provided in one of the object files or libraries that will be linked together with this object file output in the link phase. Note also that since print. Yes, I can declare them as:. If we include print. The file is named c-main. It exports main and imports printSumFloat and printSumInt , as expected.
But since one header can include other headers, the same header can indirectly be included multiple times. The difference is that, in guarded. Note that this process happens for every source file that we compile. Any macros in the actual argument are expanded before the directive replaces the formal parameter. The operators are described in Preprocessor operators. The following examples of macros with arguments illustrate the second form of the define syntax:. Arguments with side effects sometimes cause macros to produce unexpected results.
A given formal parameter may appear more than one time in token-string. If that formal parameter is replaced by an expression with side effects, the expression, with its side effects, may be evaluated more than one time. See the examples under Token-Pasting Operator. The undef directive causes an identifier's preprocessor definition to be forgotten.
See The undef Directive for more information. If the name of the macro being defined occurs in token-string even as a result of another macro expansion , it is not expanded.
A second define for a macro with the same name generates a warning unless the second token sequence is identical to the first. In other words, the two definitions can have different parameter names. For example, the following two macros are identical except for the parameter names. A string literal in the form "hh:mm:ss" containing the time at which the compilation process began. An integer value. Note that many compilers are not fully conforming and thus will have this constant defined as neither of the values above.
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