/* * File: genlib.c * Last modified on Sun Jul 24 10:29:46 1994 by eroberts * ----------------------------------------------------- * This file implements the general C library package.  See the * interface description in genlib.h for details. */#include <stdio.h>#include <stddef.h>#include <string.h>#include <stdarg.h>#include "genlib.h"#include "gcalloc.h"#include "exception.h"/* * Constants: * ---------- * ErrorExitStatus -- Status value used in exit call * MaxErrorMessage -- Longest error message allowed */#define ErrorExitStatus 1#define MaxErrorMessage 500/* Section 1 -- Define new "primitive" types *//* * Constant: UNDEFINED * ------------------- * This entry defines the target of the UNDEFINED constant. */char undefined_object[] = "UNDEFINED";/* Section 2 -- Memory allocation *//* * Implementation notes: * --------------------- * The code for the memory allocator is divided between * genlib.c and gcalloc.c, and the division strategy may at * first seem unnatural, since the function ProtectBlock is * declared in gcalloc.h but defined here in genlib.c.  The * intention is to minimize the size of object files * produced by linkers that search a library for modules * that are actually referenced.  The libraries themselves * need to call ProtectBlock (usually through the macro * ProtectVariable), but will not require the actual code * for the allocator unless InitGCAllocator is explicitly * called. *//* * Global variable: _acb * --------------------- * This variable is used to hold a method suite that makes it * easy to substitute a garbage-collecting allocator for the * ANSI allocator. */_GCControlBlock _acb = NULL;/* Memory allocation implementation */void *GetBlock(size_t nbytes){    void *result;    if (_acb == NULL) {        result = malloc(nbytes);    } else {        result = _acb->allocMethod(nbytes);    }    if (result == NULL) Error("No memory available");    return (result);}void FreeBlock(void *ptr){    if (_acb == NULL) {        free(ptr);    } else {        _acb->freeMethod(ptr);    }}void ProtectBlock(void *ptr, size_t nbytes){    if (_acb != NULL) _acb->protectMethod(ptr, nbytes);}/* Section 3 -- Basic error handling *//* * Implementation notes: Error * --------------------------- * Writing the Error function requires some care, since it is * called in circumstances in which parts of the system may be * broken.  In particular, it is not acceptable for Error to * call GetBlock, since the error condition may be that the * system is out of memory, in which case calling GetBlock would * fail.  The error string should be allocated dynamically, * so that this function can be used in reentrant code. * Note that it is critical to exit if the length bound for * an error message is exceeded, since this error almost * certainly corrupts the stack. */void Error(string msg, ...){    va_list args;    char errbuf[MaxErrorMessage + 1];    string errmsg;    int errlen;    va_start(args, msg);    vsprintf(errbuf, msg, args);    va_end(args);    errlen = strlen(errbuf);    if (errlen > MaxErrorMessage) {        fprintf(stderr, "Error: Error Message too long\n");        exit(ErrorExitStatus);    }    if (_acb == NULL) {        errmsg = malloc(errlen + 1);    } else {        errmsg = _acb->allocMethod(errlen + 1);    }    if (errmsg == NULL) {        errmsg = "No memory available";    } else {        strcpy(errmsg, errbuf);    }    if (HandlerExists(&ErrorException)) {        RaiseException(&ErrorException, "ErrorException", errmsg);    } else {        fprintf(stderr, "Error: %s\n", errmsg);        exit(ErrorExitStatus);    }}