我在Visual Studio 2010,2008和Codeblock 10.2（gcc 4.x.x）下测试了这个程序，它运行得很好。但是，当我连接到我的学校编译器时，他们使用gcc 3.3.4，它崩溃了，结果是Memory fault（coredump），我不明白为什么？我不知道是gcc 3.3.4的bug吗？或者出了什么问题？有什么想法吗？
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
const int MEM_SIZE = 65536;
/* Cache definition */
struct _tag_cache {
int tag;
int *block;
};
typedef struct _tag_cache cache;
/* Function Prototype */
void set_params( int* , int* , int* );
void program();
void display_options();
int get_val_with_mess( const char* );
int *init_main_mem_of( int );
cache *init_cache_of( int );
void free_cache( cache** , int );
void write_cache( int* , cache* , int , int , int );
void read_cache( int* , cache* , int , int , int );
void show_content( int* , int );
/* Main Program */
int main() {
program();
printf( "\nGoodbye!\n" );
return 0;
}
/* Function Implementations */
void set_params( int *main_mem_size, int *cache_size, int *block_size ) {
*main_mem_size = get_val_with_mess( "Enter main memory size (words): " );
*cache_size = get_val_with_mess( "Enter cache size (words): " );
*block_size = get_val_with_mess( "Enter block size (words/block): " );
}
void program() {
int user_option = 0;
int main_mem_size = 65536;
int cache_size = 1024;
int block_size = 16;
int tags = main_mem_size / cache_size;
int *main_mem_ptr = NULL;
cache *cache_ptr = NULL;
// initialize memory
main_mem_ptr = init_main_mem_of( main_mem_size );
cache_ptr = init_cache_of( cache_size );
do {
// display menu
display_options();
// get user input
user_option = get_val_with_mess( "\nEnter selection: " );
switch( user_option ) {
case 1:
// if user set new parameters, free old memory
free_cache( &cache_ptr, tags );
free( main_mem_ptr );
// get new sizes
set_params( &main_mem_size, &cache_size, &block_size );
// calculate number of tags
tags = main_mem_size / cache_size;
// initialize new memory
main_mem_ptr = init_main_mem_of( main_mem_size );
cache_ptr = init_cache_of( cache_size );
break;
case 2:
read_cache( main_mem_ptr, cache_ptr, main_mem_size, block_size, cache_size );
break;
case 3:
write_cache( main_mem_ptr, cache_ptr, main_mem_size, block_size, cache_size );
break;
case 4:
break;
default:
printf( "Invalid options. Try again!\n" );
break;
}
}
while( user_option != 4 );
// free cache
if( cache_ptr != NULL ) {
free_cache( &cache_ptr, tags );
}
// free memory
if( main_mem_ptr != NULL ) {
//printf( "\nFreeing main memory.\n" );
free( main_mem_ptr );
}
}
void display_options() {
printf( "\nMain memory to cache memory mapping: \n" );
printf( "------------------------------------ \n" );
printf( "1) Set parameters \n" );
printf( "2) Read cache \n" );
printf( "3) Write to cache \n" );
printf( "4) Exit \n" );
}
int get_val_with_mess( const char *user_message ) {
int var;
printf( user_message );
scanf( "%d", &var );
return var;
}
int* init_main_mem_of( int size ) {
int i = 0;
int* p = ( int* )malloc( size * sizeof( int ) );
for( ; i < size; ++i )
*( p + i ) = size - i;
return p;
}
cache* init_cache_of( int tags ) {
int i = 0;
// one cache has 64 blocks
// one block has 16 words
cache* p = ( cache* )malloc( tags * sizeof( cache ) );
for( ; i < tags; ++i ) {
p[i].tag = -1;
p[i].block = NULL;
}
return p;
}
void free_cache( cache **p, int size ) {
int i = 0;
for( ; i < size; ++i ) {
// if that block is not NULL, free it
if( ( *p )[i].block != NULL ) {
//printf( "\nFreeing block of tag %d.", i );
free( ( *p )[i].block );
}
}
// free cache
//printf( "\nFreeing cache.\n" );
free( *p );
}
void write_cache( int* main_mem_ptr, cache* cache_ptr, int mm_size, int block_size, int cache_size ) {
int addr = 0;
int value = 0;
int tag;
int block;
int word;
int i;
int base_offset;
int already_missed = 0;
addr = get_val_with_mess( "Enter main memory address to write to: " );
value = get_val_with_mess( "Enter value to write: " );
base_offset = ( addr / block_size ) * block_size;
tag = addr / cache_size;
word = addr % block_size;
block = ( addr % cache_size ) / block_size;
// assign new value
main_mem_ptr[addr] = value;
// if tag doesn't match
if( cache_ptr[block].tag != tag ) {
printf( "Write miss!\n" );
already_missed = 1;
cache_ptr[block].tag = tag;
}
// if cache block memory is NULL
if( cache_ptr[block].block == NULL ) {
if( already_missed == 0 )
printf( "Write miss!\n" );
// allocate block
cache_ptr[block].block = ( int* )malloc( block_size * sizeof( int ) );
}
// transfer from main memory to cache
for( i = 0; i < block_size; ++i ) {
cache_ptr[block].block[i] = main_mem_ptr[base_offset + i];
}
printf( "Word %d of block %d with tag %d contains %d\n", word, block, tag, cache_ptr[block].block[word] );
}
void read_cache( int* main_mem_ptr, cache* cache_ptr, int mm_size, int block_size, int cache_size ) {
int addr = 0;
int value = 0;
int tag;
int block;
int word;
int i;
int base_offset;
int already_missed = 0;
addr = get_val_with_mess( "Enter main memory address to read from: " );
base_offset = ( addr / block_size ) * block_size;
tag = addr / cache_size;
word = addr % block_size;
block = ( addr % cache_size ) / block_size;
// if tag doesn't match
if( cache_ptr[block].tag != tag ) {
printf( "Read miss!\n" );
already_missed = 1;
cache_ptr[block].tag = tag;
}
if( cache_ptr[block].block == NULL ) {
if( already_missed == 0 )
printf( "Read miss!\n" );
// allocate block
cache_ptr[block].block = ( int* )malloc( block_size * sizeof( int ) );
}
// read from main memory
for( i = 0; i < block_size; ++i ) {
cache_ptr[block].block[i] = main_mem_ptr[base_offset + i];
}
printf( "Word %d of block %d with tag %d contains %d\n", word, block, tag, cache_ptr[block].block[word] );
}
void show_content( int* p, int size ) {
int i = 0;
for( ; i < size; ++i )
printf( "%d, ", p[i] );
}
输入和输出样本
Main memory to Cache memory mapping:
--------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 1
Enter main memory size (words): 65536
Enter cache size (words): 1024
Enter block size (words/block): 16
Main memory to Cache memory mapping:
--------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 3
Enter main memory address to write to: 65535
Enter value to write: 14
Write miss!
Word 15 of block 63 with tag 63 contains value 14
Main memory to Cache memory mapping:
--------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 2
Enter main memory address to read from: 65535
Word 15 of block 63 with tag 63 contains value 14
Main memory to Cache memory mapping:
--------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 3
Enter main memory address to write to: 65534
Enter value to write: 512
Word 14 of block 63 with tag 63 contains value 512
Main memory to Cache memory mapping:
--------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 2
Enter main memory address to read from: 1023
Read miss!
Word 15 of block 63 with tag 0 contains value 64513
Main memory to Cache memory mapping:
--------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 4
%
答案 0 :(得分：2)
我没有完成整个计划，但我发现的第一件事就是当你致电malloc()时，你没有检查是否成功。
e.g。
int* init_main_mem_of(int size)
{
int i = 0;
int* p = (int *)malloc(size * sizeof(int));
if (!p)
{
puts("Error: Out of memory\n");
exit(1);
}
for( ; i < size; ++i)
p[i] = size - i;
return p;
}
问题可能是学校计算机内存耗尽，而不是编译器。完成程序并确保每次malloc()的调用都成功。
答案 1 :(得分：2)
aschelper从截图中捕获了错误。您指定的内存大小为65535，然后告诉它在地址65535处写入（超出数组末尾！）。
在valgrind中运行时，会发生以下输出（使用gcc-4.5.2编译）：
$ valgrind ./test
==29640== Memcheck, a memory error detector
==29640== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==29640== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==29640== Command: ./test
==29640==
Main memory to cache memory mapping:
------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 1
Enter main memory size (words): 65535
Enter main memory size (words): 1024
Enter block size (words/block): 16
Main memory to cache memory mapping:
------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: 3
Enter main memory address to write to: 65535
Enter value to write: 14
==29640== Invalid write of size 4
==29640== at 0x400B25: write_cache(int*, _tag_cache*, int, int, int) (test.cc:173)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac4bc is 0 bytes after a block of size 262,140 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x400968: init_main_mem_of(int) (test.cc:122)
==29640== by 0x400824: program() (test.cc:71)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
==29640== Invalid read of size 4
==29640== at 0x400B34: write_cache(int*, _tag_cache*, int, int, int) (test.cc:175)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac8f0 is 0 bytes after a block of size 1,008 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x4009C8: init_cache_of(int) (test.cc:132)
==29640== by 0x400832: program() (test.cc:72)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
Write miss!
==29640== Invalid write of size 4
==29640== at 0x400B5C: write_cache(int*, _tag_cache*, int, int, int) (test.cc:178)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac8f0 is 0 bytes after a block of size 1,008 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x4009C8: init_cache_of(int) (test.cc:132)
==29640== by 0x400832: program() (test.cc:72)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
==29640== Invalid read of size 8
==29640== at 0x400B6B: write_cache(int*, _tag_cache*, int, int, int) (test.cc:181)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac8f8 is 8 bytes after a block of size 1,008 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x4009C8: init_cache_of(int) (test.cc:132)
==29640== by 0x400832: program() (test.cc:72)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
==29640== Invalid write of size 8
==29640== at 0x400BA5: write_cache(int*, _tag_cache*, int, int, int) (test.cc:185)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac8f8 is 8 bytes after a block of size 1,008 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x4009C8: init_cache_of(int) (test.cc:132)
==29640== by 0x400832: program() (test.cc:72)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
==29640== Invalid read of size 8
==29640== at 0x400BBF: write_cache(int*, _tag_cache*, int, int, int) (test.cc:189)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac8f8 is 8 bytes after a block of size 1,008 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x4009C8: init_cache_of(int) (test.cc:132)
==29640== by 0x400832: program() (test.cc:72)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
==29640== Invalid read of size 4
==29640== at 0x400BE4: write_cache(int*, _tag_cache*, int, int, int) (test.cc:189)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac4bc is 0 bytes after a block of size 262,140 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x400968: init_main_mem_of(int) (test.cc:122)
==29640== by 0x400824: program() (test.cc:71)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
==29640== Invalid read of size 8
==29640== at 0x400C06: write_cache(int*, _tag_cache*, int, int, int) (test.cc:192)
==29640== by 0x400878: program() (test.cc:80)
==29640== by 0x4006CC: main (test.cc:29)
==29640== Address 0x59ac8f8 is 8 bytes after a block of size 1,008 alloc'd
==29640== at 0x4C24660: malloc (vg_replace_malloc.c:195)
==29640== by 0x4009C8: init_cache_of(int) (test.cc:132)
==29640== by 0x400832: program() (test.cc:72)
==29640== by 0x4006CC: main (test.cc:29)
==29640==
Word 15 of block 63 with tag 63 contains 14
Main memory to cache memory mapping:
------------------------------------
1) Set parameters
2) Read cache
3) Write to cache
4) Exit
Enter selection: ^C==29640==
==29640== HEAP SUMMARY:
==29640== in use at exit: 263,212 bytes in 3 blocks
==29640== total heap usage: 5 allocs, 2 frees, 526,380 bytes allocated
==29640==
==29640== LEAK SUMMARY:
==29640== definitely lost: 64 bytes in 1 blocks
==29640== indirectly lost: 0 bytes in 0 blocks
==29640== possibly lost: 0 bytes in 0 blocks
==29640== still reachable: 263,148 bytes in 2 blocks
==29640== suppressed: 0 bytes in 0 blocks
==29640== Rerun with --leak-check=full to see details of leaked memory
==29640==
==29640== For counts of detected and suppressed errors, rerun with: -v
==29640== ERROR SUMMARY: 23 errors from 8 contexts (suppressed: 4 from 4)
你很幸运，它没有与其他编译器崩溃，但你确实有错误（你没有检查用户输入是否正确！）
至少，也许你应该在main_mem_ptr[addr] = value;：
assert(addr < main_mem_size);
答案 2 :(得分：2)
如果您在源代码级调试器 - gdb。
下运行程序，您始终可以获得有关崩溃的信息使用-g选项编译源代码并在gdb下运行。
$ gdb ./your_prog_name_here
在gdb中输入“run”来启动程序。
当程序崩溃时，gdb将停止。键入“bt”以获取可执行文件的回溯，以了解哪个语句导致崩溃。
希望得到这个帮助。