我正在使用 fgets() 从文件中读取行。我能够读取文件的几行，然后 fgets() 返回访问冲突。人们会认为我的文件缓冲区存在问题，但正如您在我的代码中看到的那样，情况并非如此。我注意到的一个奇怪行为是，如果我在一个紧密的循环中读取并打印文件的所有行，我就没有问题。我使用了一些 printf() 语句来调试这个问题，并注意到文件位置因执行哪个循环而异。我的“完整循环”逻辑中没有触及 FILE *。
紧密循环文件位置为：0、27、53、80、82、99、127、155 等。
完整的循环文件位置：0、27、53、80、82、99、138
输入文件：
!!!!!!!!!!!!!!!!!!!!!!!!!
! Test sparc gagdet file
!!!!!!!!!!!!!!!!!!!!!!!!!
! instruction 1
1: subcc %g0, %i4, %i4
1: subc %g0, %i4, %i4 ** access violation reading this line **
! instruction 2
** etc. **
代码：
/*
* parse_profile: Parse the gadget profile and load the memory structures required to scan the library file
*/
int parse_profile(FILE * gadget_file, struct g_handle * gadget_handle){
// Buffers used to temporarily store file imput
char op_code [NODE_BUF_SIZE] = "\0";
char reg [NODE_BUF_SIZE] = "\0";
// Reference nodes in the bod_ops and save_regs lists
struct char_node * temp_node = NULL;
struct char_node * op_node = NULL;
struct char_node * reg_node = NULL;
//
int level = 1;
int old_level = 1;
int curr_line = 0;
// A buffer to hold file data
char file_buffer [PAGE_SIZE];
// Reference nocdes in the instruction tree
struct instruction_node * current_node = NULL;
struct instruction_node * prev_node = NULL;
struct instruction_node * prev_level = NULL;
// Read a line from the gadget file (data for a single instruction)
//while(fgets(file_buffer, PAGE_SIZE, gadget_file) != NULL){
char * shiz = file_buffer;
while(shiz != NULL){
printf("\n file location: %d", ftell(gadget_file));
fflush(stdout);
shiz = fgets(file_buffer, PAGE_SIZE, gadget_file);
/*
// tight loop with different file position
while(shit != NULL){
printf("\n file location: %d", ftell(gadget_file));
fflush(stdout);
shiz = fgets(file_buffer, PAGE_SIZE, gadget_file);
}
*/
// Increment the current line
curr_line = curr_line + 1;
printf("\nline (%d)", curr_line);
fflush(stdout);
// Ensure we have gathered the entire line of the file
if(strlen(file_buffer) >= PAGE_SIZE){
// We have exceeded the maximum line size, quit
printf("\nError reading gadget profile, Line %d: Maximum line length of 4096 has been exceeded", curr_line);
return(-1);
} // Ensure we have gathered the entire line of the file
// If this is a comment
if(*file_buffer == '!'){
// Do nothing
}
// If this is a blank line
else if(sscanf(file_buffer," %s ") < 1){
// Do nothing
}
// Scan the current line until we have saved all instructions
else if(sscanf(file_buffer,"%d: %s", &level, op_code) == 2){
printf("\n file location: %d", ftell(gadget_file));
fflush(stdout);
printf("1");
fflush(stdout);
// Store instruction information
/*
commented block
*/
} // Scan the current line until we have saved all instruction/nibble pairs
// Scan the current line until we have saved all registers to be preserved
else if(sscanf (file_buffer,"r: %s", reg) == 1){
/*
commented block
*/
} // Scan the current line until we have saved all registers to be preserved
// Scan the current line until we have saved all op_codes to be avoided
else if(sscanf (file_buffer,"o: %s", op_code) == 1){
/*
commented block
*/
} // Scan the current line until we have saved all op_codes to be avoided
else{
// quit
printf("\nError reading gadget profile, Line %d: \n%s", curr_line, file_buffer);
return(-1);
}
printf("7");
printf("\n file location: %d", ftell(gadget_file));
fflush(stdout);
} // Read a line from the gadget file (data for a single instruction)
printf("a");
fflush(stdout);
// If fread() returned an error, exit with an error
if(ferror(gadget_file) != 0){
// Print error and exit
printf("\nError reading gadget profile");
return(-1);
} // If fread() returned an error, exit with an error
return 0;
}