【发布时间】：2011-05-09 16:39:37
【问题描述】：
我是 C 新手，但在使用动态内存时遇到问题。 我 malloc 结构图，然后根据需要重新分配。当我试图调试我的代码时，我注意到在 ddd 的帮助下我覆盖了前一个数字（在我提供的第二块代码中 - 变量的名称是 figureHere）。如果有人能看到我愚蠢错误的原因，请告诉我。
第一个代码块在第二个代码块中调用了一个 void。
#include <assert.h>
#include "draw2.h"
#include "draw2a.h"
#include "draw2b.h"
const char Exec_c[] = "java -jar Sketchpad.jar";
void parseFile(FILE * fp, FILE *sketcher){
char line [MAX_WORD] = {"NULL"};
char word [MAX_WORD] = {"NULL"};
char figureName [MAX_WORD] = {"NULL"};
struct figure *pointsAndname;
int countNumberoffigures = 0; //accounts to which figure in the array we are on
printOutput();
int temp = 0;
pointsAndname = malloc(temp);
assert(pointsAndname != NULL);
while ( fgets(line, MAX_WORD - 1, fp) != NULL ){
int nuRead = sscanf(line, "%s", word);
assert(pointsAndname != NULL);
if ( nuRead > 0 ){
if(strncmp(word, "Figure", MAX_WORD)==0){ //1)reads the figure, name and the two starting points
countNumberoffigures += 1;
assert(pointsAndname != NULL);
figureFunction(fp,line, word, figureName, countNumberoffigures, pointsAndname + countNumberoffigures - 1);
if (temp <= countNumberoffigures){
temp += sizeof(struct figure);
pointsAndname = realloc(pointsAndname, temp);
}
}
if(strncmp(word, "printFigure", MAX_WORD)==0){ //4)read the command printFigure, name of the figure
printFigure(fp, line, countNumberoffigures, pointsAndname + countNumberoffigures - 1);
}
if(strncmp(word, "drawFigure", MAX_WORD)==0){ //5)read the command drawFigure and the name of the figure
drawFigure(sketcher, line, countNumberoffigures);
}
if(strncmp(word, "translate", MAX_WORD)==0){ //6)read the command translate
translate(line, sketcher, countNumberoffigures);
}
if(strncmp(word, "child", MAX_WORD)==0){ //7)reads command child and the name of the figure
child(line, word, figureName, sketcher);
}
if(strncmp(word, "#", MAX_WORD)==0){ //8)reads the whole line until the \n
printf(line);
}
if(strncmp(word, "end", MAX_WORD)==0){
fprintf (sketcher, "end\n");
}
if(strncmp(word, "rotate", MAX_WORD)==0){
rotate(line, sketcher, countNumberoffigures);
}
}
}
}
void processArgument(char argument[]){
FILE *sketcher;
FILE *fp;
fp = fopen (argument, "r");
sketcher = popen(Exec_c, "w");
if (fp == NULL){
printf ("Could not open pipe to %s\n", argument);
exit (EXIT_FAILURE);
}
if (sketcher == NULL){
printf ("Could not open pipe to %s\n", argument);
exit (EXIT_FAILURE);
}else{
parseFile(fp, sketcher);
if(fclose(fp)==EOF){
printf("couldn't close pipe to %s.\n", argument);
exit(EXIT_FAILURE);
}
if (pclose(sketcher) == -1){
fprintf(stderr, "draw_line error: couldn't close pipe to %s.\n", Exec_c);
exit(EXIT_FAILURE);
}
}
}
int main (int argc, char *argv[]){
int i;
if ( argc < 2 ){
printf ("%s\n", "0 comment(s)");
exit(EXIT_FAILURE);
}else{
for (i = 1; i < argc; i++){
processArgument(argv[i]);
}
}
return 0;
}
#include "draw2.h"
#include "draw2a.h"
void printOutput(){
printf("./draw2 started on:");
fflush(stdout);
system("date\n");
}
/*send what ever there is after the child to sketchpad(in that specific line)*/
void child (char line[], char word[], char nameFigure[], FILE * sketcher){
sscanf(line, "%s%s", word, nameFigure);
fprintf (sketcher, "%s\n", &line[6]);
}
/*I construct the struct by reading from the Figure line to the end figure line.*/
void figureFunction (FILE * fp, char line[], char word[], char figureName[], int countNumberoffigures, struct figure *figureHere){
double startx, starty;
int temp = 0;
printf("The line: %s", line);
figureHere->vertices = malloc(temp);
sscanf(line, "%s%s%lf%lf%*s", word, figureHere->figureName, &startx, &starty);
(*(figureHere->vertices)).x = startx;
(*(figureHere->vertices)).y = starty;
printf("I'm in side figureFunction and this is my figureHere->figureName = %s\n\n", figureHere->figureName);
fgets(line, MAX_WORD - 1, fp);
int nuRead = sscanf(line, "%s", word); //until the line with End Figure I construct my points of figure.
int i = 1;
while (strncmp(word, "End", MAX_WORD)!=0){
if (strncmp(word, "#", MAX_WORD) == 0){
printf("%s",line);
}
if (strncmp(word, "draw", MAX_WORD) == 0){
sscanf (line, "%s%lf%lf", word, &startx, &starty);
figureHere->vertices[i].x = figureHere->vertices[i-1].x + startx;
figureHere->vertices[i].y = figureHere->vertices[i-1].y + starty;
i += 1;
}
fgets(line, MAX_WORD - 1, fp);
nuRead = sscanf(line, "%s", word);
}
figureHere->countPoints = i;
if (temp >= figureHere->countPoints){
temp += sizeof(struct pointxy);
figureHere->vertices = realloc(figureHere->vertices, temp);
}
}
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>
void parseFile(FILE * fp, FILE * sketcher);
void processArgument(char argument[]);
void printOutput();
#define MAX_WORD 256
#define initial_size 17
extern const char argument[];
/* prototypes for non-c99 library functions */
FILE* popen(const char*, const char*);
int pclose(FILE*);
struct pointxy {
double x;
double y;
};
struct figure{
//struct figure *nextfigure;
char figureName[MAX_WORD];
struct pointxy *vertices;
int countPoints;
};
struct figure *figurehere;
【问题讨论】：
-
将来，您应该尝试将示例代码简化到仍然会产生错误的最小量。这甚至可以帮助您自己解决问题。