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dyncall(3)


dyncall(3)


NAME

     dyncall – encapsulation of architecture-, OS- and compiler-specific
     function call semantics


SYNOPSIS

     #include <dyncall.h>

     DCCallVM *
     dcNewCallVM(DCsize size);

     void
     dcFree(DCCallVM * vm);

     void
     dcMode(DCCallVM * vm, DCint mode);

     void
     dcReset(DCCallVM * vm);

     void
     dcArgBool(DCCallVM * vm, DCbool arg);

     void
     dcArgChar(DCCallVM * vm, DCchar arg);

     void
     dcArgShort(DCCallVM * vm, DCshort arg);

     void
     dcArgInt(DCCallVM * vm, DCint arg);

     void
     dcArgLong(DCCallVM * vm, DClong arg);

     void
     dcArgLongLong(DCCallVM * vm, DClonglong arg);

     void
     dcArgFloat(DCCallVM * vm, DCfloat arg);

     void
     dcArgDouble(DCCallVM * vm, DCdouble arg);

     void
     dcArgPointer(DCCallVM * vm, DCpointer arg);

     DCvoid
     dcCallVoid(DCCallVM * vm, DCpointer funcptr);

     DCbool
     dcCallBool(DCCallVM * vm, DCpointer funcptr);

     DCchar
     dcCallChar(DCCallVM * vm, DCpointer funcptr);

     DCshort
     dcCallShort(DCCallVM * vm, DCpointer funcptr);

     DCint
     dcCallInt(DCCallVM * vm, DCpointer funcptr);

     DClong
     dcCallLong(DCCallVM * vm, DCpointer funcptr);

     DClonglong
     dcCallLongLong(DCCallVM * vm, DCpointer funcptr);

     DCfloat
     dcCallFloat(DCCallVM * vm, DCpointer funcptr);

     DCdouble
     dcCallDouble(DCCallVM * vm, DCpointer funcptr);

     DCpointer
     dcCallPointer(DCCallVM * vm, DCpointer funcptr);

     void
     dcArgF(DCCallVM * vm, const DCsigchar * signature, ...);

     void
     dcVArgF(DCCallVM * vm, const DCsigchar * signature, va_list args);

     void
     dcCallF(DCCallVM * vm, DCValue * result, DCpointer funcptr,
         const DCsigchar * signature, ...);

     void
     dcVCallF(DCCallVM * vm, DCValue * result, DCpointer funcptr,
         const DCsigchar * signature, va_list args);


DESCRIPTION

     The dyncall library encapsulates architecture-, OS- and compiler-specific
     function call semantics in a virtual "bind argument parameters from left
     to right and then call" interface allowing programmers to call C
     functions in a completely dynamic manner.

     In other words, instead of calling a function directly, the dyncall
     library provides a mechanism to push the function parameters manually and
     to issue the call afterwards.

     Since the idea behind this concept is similar to call dispatching
     mechanisms of virtual machines, the object that can be dynamically loaded
     with arguments, and then used to actually invoke the call, is called
     CallVM. It is possible to change the calling convention used by the
     CallVM at run-time. Due to the fact that nearly every platform comes with
     one or more distinct calling conventions, the dyncall library project
     intends to be a portable and open-source approach to the variety of
     compiler-specific binary interfaces, platform specific subtleties, and so
     on...

     dcNewCallVM() creates a new CallVM object, where size specifies the max
     size of the internal stack that will be allocated and used to bind the
     arguments to. Use dcFree() to destroy the CallVM object.

     dcMode() sets the calling convention to use. See dyncall.h for a list of
     available modes. Note that some mode/platform combinations don't make any
     sense (e.g. using a PowerPC calling convention on a MIPS platform) and
     are silently ignored.

     dcReset() resets the internal stack of arguments and prepares it for a
     new call.  This function should be called after setting the call mode
     (using dcMode), but prior to binding arguments to the CallVM. Use it also
     when reusing a CallVM, as arguments don't get flushed automatically after
     a function call invocation.  Note: you should also call this function
     after initial creation of the a CallVM object, as dcNewCallVM doesn't do
     this, implicitly.

     dcArgBool(), dcArgChar(), dcArgShort(), dcArgInt(), dcArgLong(),
     dcArgLongLong(), dcArgFloat(), dcArgDouble() and dcArgPointer() are used
     to bind arguments of the named types to the CallVM object. Arguments
     should be bound in left to right order regarding the C function
     prototype.

     dcCallVoid(), dcCallBool(), dcCallChar(), dcCallShort(), dcCallInt(),
     dcCallLong(), dcCallLongLong(), dcCallFloat(), dcCallDouble() and
     dcCallPointer() call the function with the bound arguments and returning
     the named type, where funcptr is a pointer to the function to call. After
     the invocation of the function call, the argument values are still bound
     to the CallVM and a second call using the same arguments can be issued.
     Call reset() to clear the internal argument stack.

     dcArgF(), dcVArgF(), dcCallF() and dcVCallF() can be used to bind
     arguments in a printf-style call, using a signature string encoding the
     argument types and return type. The former 2 only bind the arguments to
     the vm object (and ignore return types specified in the signature),
     whereas the latter two issue a call to the given function pointer,
     afterwards. The return value will be stored in result.  The signature
     string also features calling convention mode selection.  For information
     about the signature format, refer to the dyncall manual in PDF format.


EXAMPLE

     Let's say, we want to make a call to the function:

                   double sqrt(double x);

     Using the dyncall library, this function would be called as follows:

                   double r;
                   DCCallVM* vm = dcNewCallVM(4096);
                   dcMode(vm, DC_CALL_C_DEFAULT);
                   dcReset(vm);
                   dcArgDouble(vm, 4.2373);
                   r = dcCallDouble(vm, (DCpointer)&sqrt);
                   dcFree(vm);


CONFORMING TO

     The dyncall library needs at least a c99 compiler with additional support
     for anonymous structs/unions (which were introduced officially in c11).
     Given that those are generally supported by pretty much all major c99
     conforming compilers (as default extension), it should build fine with a
     c99 toolchain. Strictly speaking, dyncall conforms to c11, though.


SEE ALSO

     dyncallback(3), dynload(3) and the dyncall manual (available in HTML and
     PDF format) for more information.


AUTHORS

     Daniel Adler ⟨dadler@uni-goettingen.de⟩
     Tassilo Philipp ⟨tphilipp@potion-studios.com⟩

                                April 13, 2020