私はちょうど、PHPから来て、Cの学習を始めました。私はmallocとフリーを使う方法はまだ分かりません。ダイナミックメモリ割り当てにmallocとfreeを使用する方法
1)私は "無料"を置くことができる以下の例のコードでは?
#include <stdio.h>
#include <stdlib.h>
int strLen(char* text) {
int c = 0;
for (int i = 0; text[i] != '\0'; ++i) ++c;
return c;
}
char* reverse(char* text) {
int count = strLen(text);
char* t = malloc(count);
for (int i = count; i > 0; --i) { t[count - i] = text[i-1]; }
t[count] = '\0'; /* Add end of string */
return t;
}
int main (int argc, char** argv) {
if (argc > 1) {
for (int i = 1; i < argc; ++i) {
printf("%d\t%s\t%s\n", i, argv[i], reverse(argv[i]));
}
}
return 0;
}
2)これはvalgrindのから出力されます。 「サイズ1の無効な書き込み」と「サイズ1の無効な読み取り」というエラーはどういう意味ですか?
valgrind ./reverse Text ONe
==3124== Memcheck, a memory error detector
==3124== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==3124== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==3124== Command: ./reverse Text ONe
==3124==
==3124== Invalid write of size 1
==3124== at 0x40060F: reverse (in /localServer/temp/C/reverse)
==3124== by 0x400654: main (in /localServer/temp/C/reverse)
==3124== Address 0x5203044 is 0 bytes after a block of size 4 alloc'd
==3124== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3124== by 0x4005C6: reverse (in /localServer/temp/C/reverse)
==3124== by 0x400654: main (in /localServer/temp/C/reverse)
==3124==
==3124== Invalid read of size 1
==3124== at 0x4E88CC0: vfprintf (vfprintf.c:1632)
==3124== by 0x4E8F898: printf (printf.c:33)
==3124== by 0x400682: main (in /localServer/temp/C/reverse)
==3124== Address 0x5203044 is 0 bytes after a block of size 4 alloc'd
==3124== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3124== by 0x4005C6: reverse (in /localServer/temp/C/reverse)
==3124== by 0x400654: main (in /localServer/temp/C/reverse)
==3124==
1 Text txeT
2 ONe eNO
==3124==
==3124== HEAP SUMMARY:
==3124== in use at exit: 7 bytes in 2 blocks
==3124== total heap usage: 3 allocs, 1 frees, 1,031 bytes allocated
==3124==
==3124== LEAK SUMMARY:
==3124== definitely lost: 7 bytes in 2 blocks
==3124== indirectly lost: 0 bytes in 0 blocks
==3124== possibly lost: 0 bytes in 0 blocks
==3124== still reachable: 0 bytes in 0 blocks
==3124== suppressed: 0 bytes in 0 blocks
==3124== Rerun with --leak-check=full to see details of leaked memory
==3124==
==3124== For counts of detected and suppressed errors, rerun with: -v
==3124== ERROR SUMMARY: 4 errors from 2 contexts (suppressed: 0 from 0)
ありがとうございます。
クイックフードと女の子がそれをやる方法です。 upvoteをしてください。 – Bathsheba