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Top Forums Programming Conditions/suggestions to use shared library in C/C++ coding Post 303017464 by Corona688 on Wednesday 16th of May 2018 11:11:22 AM
Old 05-16-2018
Quote:
Originally Posted by yifangt
What are the basic conditions to use other people's library in C/C++ coding?
It's simpler than you think. The compiler only needs to know that these functions exist to use them.

Which is why a proper C header file is full of declarations like this:

Code:
int functionname(int x, long y, void *z);

...along with the data types they need, of course.

C++ ones will look a little more like:

Code:
class myclassname {
public:
        // Most functions won't be defined right in the declaration
        myclassname();

        // Smaller functions may be defined here but MUST be inline
        inline int myfunction(void) { function_contents(); }
};

Quote:
Here I do not mean the compiling step, but at the step of writing source code (from scratch in a way!).
#include <header.h> for the compiler, and -lsomelibraryname for the linker, are really all that's required in the vast majority of cases. The compiler generates the giant pile of names the linker needs to look for, and the linker searches through all default plus requested libraries to turn these name-stubs into addresses a program can use.
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FORT77(1)						     Linux Programmer's Manual							 FORT77(1)

NAME
fort77 - invoke f2c Fortran translator transparently, like a compiler SYNOPSIS
fort77 [-c] [-g] [-v] [-k] [-P] [-cpp] [f2c option ...] [-L directory ...] [gcc-option ...] [link option ...] [-O optlevel] [-o out- file] [-s] [-w] [-Wx,arg1[,arg2]...] file ... DESCRIPTION
The fort77 script invokes the f2c command transparently, so it can be used like a real Fortran compiler. It can be used to compile For- tran, C and assembler code, and to link it with the f2c libraries. File arguments ending with .f are compiled as Fortran source files. Files which end with .P are passed through to f2c, and files ending with .F are passed to the C preprocessor (invoked as "/lib/cpp -traditional") first. Any switches passed via -D will be passed to the pre- processor. If the translation is successful, the resulting C files will be passed to cc for translation into an object file. Files ending in .c, .C, .cc, .i, .s, .S, .m, .cc or .cxx are passed to the GNU C compiler directly; see gcc(1). All other files are passed to the linker. OPTIONS
-c Supress linking and produce an object ( .o ) file from each source file. -g Include debugging information. -v Be verbose; supplying this twice will also tell the C compilers etc to be verbose. -k Keep the C files generated by f2c around. -cpp Pass Fortran code through the C preprocessor, as if filenames ended in .F. -P Generate f2c .P files. -Ldirectory Include directory in the search for libraries in the final linking stage. -o outfile Send output to outfile. -trapuv Have f2c generate code to trap uninitialized values. -Wx,arg1[,arg2...] Pass the argument[s] argi through to the subprocess x, where x can assume one of the following values: f for the f2c step, p for the preprocessing step, c for the C compiler, a for the assembler (this is actually passed to the C compiler, too), and l for the linker. As an example, defining a preprocessor constant for the C compilation step would be done with -Wc,-DUNIX=1. Specifying the -f option to f2c would be done via -Wf,-f. f2c option fort77 passes through almost all f2c options: -C, -U, -u, -a, -E, -h, -P, -R, -r, -z, -I2, -I4, -onetrip, -!c, -!l, -!P, -!R, -ext, -!bs, -W[n], -trapuv, -w8, -r8 and -w66. gcc options The following options are passed through to gcc: -f*, -W*, -U*, -A*, -m*, -S, -E, -v, -x, -pipe, -o, -I, -V, -b*, -p, -pg. linker option The options passed to the linking stage are -static, -shared, -v, -V, and -symbolic. BUGS
To make debugging work, you need to set a breakpoint at MAIN__ before you start. f2c This script automatically supplies the -I. option to f2c. Older versions of f2c may not support this. This script is for the interaction of gcc and f2c; using it with another compiler will probably require modification. The fort77 script does not strictly conform to Posix.2, because it acceppts long options with one leading slash. This is done for gcc com- patibility. SEE ALSO
f2c(1), cc(1), as(1), ld(1) AUTHOR
Thomas Koenig, ig25@rz.uni-karlsruhe.de Linux Nov 1996 FORT77(1)
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