Void-Zeiger, Speicherbelegung und valgrind

Question

Ich habe dieses Stück Code:

void *data = calloc(1, sizeof(char)+sizeof(float)+sizeof(char)); // line 56 

*((char *) data) = 'a'; // line 58 
*((float *) data + sizeof(char)) = 0.2f; // line 59 
*((char *) data + sizeof(float) + sizeof(char)) = 'a'; // line 60 

printf("%c ", *((char *) data)); // line 62 
printf("%f ", *((float *) data + sizeof(char))); // line 63 
printf("%c ", *((char *) data + sizeof(float) + sizeof(char))); // line 64 
printf("\n"); 

Und basicly was ich versuche, in den gleichen Speicherbereich verschiedene Arten von Variablen und ihre Werte zu tun ist, zu speichern. Um das zu tun, benutze ich void Zeiger und Offsets von Variablen, und alles funktioniert gut, ABER, valgrind sagt mir immer wieder, dass ich ungültige Lese- und Schreibvorgänge habe und ich verstehe nicht warum. Alles macht meiner Meinung nach Sinn, aber Valgrind ist anderer Meinung.

Hier ist valgrind der Ausgabe:

==5829== Memcheck, a memory error detector 
==5829== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al. 
==5829== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info 
==5829== Command: ./a.out 
==5829== 
==5829== Invalid write of size 4 
==5829== at 0x400909: main (Main.c:59) 
==5829== Address 0x51f6044 is 4 bytes inside a block of size 6 alloc'd 
==5829== at 0x4C2AA98: calloc (vg_replace_malloc.c:711) 
==5829== by 0x4008ED: main (Main.c:56) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E83CEE: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E83ED6: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E7D9C0: __mpn_extract_double (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E843C9: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E83FFA: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E845E2: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E85504: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C2E8: __mpn_lshift (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85508: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C2EB: __mpn_lshift (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85508: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E85546: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E85568: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E856CC: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E85A54: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C904: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85A6F: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C98F: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85A6F: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7CA02: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85A6F: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E85A83: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E85A92: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C3F8: __mpn_rshift (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85DF1: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C41D: __mpn_rshift (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85DF1: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E849F1: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C904: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E849F8: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C928: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E849F8: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84A40: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E836D9: hack_digit (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E84A58: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C904: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E836E0: hack_digit (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E84A58: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Use of uninitialised value of size 8 
==5829== at 0x4E7C928: __mpn_mul_1 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E836E0: hack_digit (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E84A58: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84A63: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84A71: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E85093: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E85099: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E853BD: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E853E2: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E8541D: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84BDF: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84E36: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84FF9: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E84FDB: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4EAFC4D: _IO_file_overflow@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85C90: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4EAFC7A: _IO_file_overflow@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E85C90: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Conditional jump or move depends on uninitialised value(s) 
==5829== at 0x4E85C94: __printf_fp (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E82D9D: vfprintf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4E88D28: printf (in /usr/lib64/libc-2.22.so) 
==5829== by 0x400951: main (Main.c:63) 
==5829== 
==5829== Syscall param write(buf) points to uninitialised byte(s) 
==5829== at 0x4F27C10: __write_nocancel (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4EAE14E: _IO_file_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4EAF8F8: _IO_do_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4EAFD0A: _IO_file_overflow@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so) 
==5829== by 0x4EA6A47: putchar (in /usr/lib64/libc-2.22.so) 
==5829== by 0x40097A: main (Main.c:65) 
==5829== Address 0x4022004 is in a rw- anonymous segment 
==5829== 
a 0.199592 a 
==5829== 
==5829== HEAP SUMMARY: 
==5829==  in use at exit: 6 bytes in 1 blocks 
==5829== total heap usage: 1 allocs, 0 frees, 6 bytes allocated 
==5829== 
==5829== LEAK SUMMARY: 
==5829== definitely lost: 6 bytes in 1 blocks 
==5829== indirectly lost: 0 bytes in 0 blocks 
==5829==  possibly lost: 0 bytes in 0 blocks 
==5829== still reachable: 0 bytes in 0 blocks 
==5829==   suppressed: 0 bytes in 0 blocks 
==5829== Rerun with --leak-check=full to see details of leaked memory 
==5829== 
==5829== For counts of detected and suppressed errors, rerun with: -v 
==5829== Use --track-origins=yes to see where uninitialised values come from 
==5829== ERROR SUMMARY: 103 errors from 42 contexts (suppressed: 0 from 0) 

Wenn mich jemand darüber geben könnte, warum valgrind so wütend ist, wäre es toll.

Vielen Dank!

Answer 1

Valgrind ist wütend, weil Sie die falschen Adressen verwenden.

Ihre Aussagen sind alle mit Zeiger arithmetics, das ist nicht Integer-Arithmetik.

Zum Beispiel:

*((float *) data + sizeof(char)) 

Fügt man float bemessen ist, um Offset-Daten, nicht "1".

Sie benötigen die richtigen Zeigertypen für Ihre Arithmetik, und nachdem Sie den korrekten Offset berechnet haben, müssen Sie den gewünschten Typ verwenden.