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PO"Use of uninitialised value" despite of memset
 

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  1. PO"Use of uninitialised value" despite of memset
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    <p>I allocate a 2d array and use memset to fill it with zeros.</p> <pre><code>#include&lt;stdio.h&gt; #include&lt;string.h&gt; #include&lt;stdlib.h&gt; void main() { int m=10; int n =10; int **array_2d; array_2d = (int**) malloc(m*sizeof(int*)); if(array_2d==NULL) { printf("\n Could not malloc 2d array \n"); exit(1); } for(int i=0;i&lt;m;i++) { ((array_2d)[i])=malloc(n*sizeof(int)); memset(((array_2d)[i]),0,sizeof(n*sizeof(int))); } for(int i=0; i&lt;10;i++){ for(int j=0; j&lt;10;j++){ printf("(%i,%i)=",i,j); fflush(stdout); printf("%i ", array_2d[i][j]); } printf("\n"); } } </code></pre> <p>Afterwards I use valgrind [1] to check for memory errors. I get following error: <code>Conditional jump or move depends on uninitialised value(s)</code> for line 24 (<code>printf("%i ", array_2d[i][j]);</code>). I always thought memset is the function to initialize arrays. How can I get rid off this error?</p> <p>Thanks!</p> <p>Valgrind output:</p> <pre><code>==3485== Memcheck, a memory error detector ==3485== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al. ==3485== Using Valgrind-3.5.0-Debian and LibVEX; rerun with -h for copyright info ==3485== Command: ./a.out ==3485== (0,0)=0 (0,1)===3485== Use of uninitialised value of size 4 ==3485== at 0x409E186: _itoa_word (_itoa.c:195) ==3485== by 0x40A1AD1: vfprintf (vfprintf.c:1613) ==3485== by 0x40A8FFF: printf (printf.c:35) ==3485== by 0x8048724: main (playing_with_valgrind.c:39) ==3485== ==3485== ==3485== ---- Attach to debugger ? --- [Return/N/n/Y/y/C/c] ---- ==3485== Conditional jump or move depends on uninitialised value(s) ==3485== at 0x409E18E: _itoa_word (_itoa.c:195) ==3485== by 0x40A1AD1: vfprintf (vfprintf.c:1613) ==3485== by 0x40A8FFF: printf (printf.c:35) ==3485== by 0x8048724: main (playing_with_valgrind.c:39) </code></pre> <p>[1] <code>valgrind --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes --db-attach=yes ./a.out</code></p> <p>[gcc-cmd] <code>gcc -std=c99 -lm -Wall -g3 playing_with_valgrind.c</code></p>
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      1. PO"Use of uninitialised value" despite of memset
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      1. PO"Use of uninitialised value" despite of memset
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    1. This table or related slice is empty.
 

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