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POProgram using read() entering into an infinite loop
 

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  1. POProgram using read() entering into an infinite loop
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    <pre><code>1oid ReadBinary(char *infile,HXmap* AssetMap) { int fd; size_t bytes_read, bytes_expected = 100000000*sizeof(char); char *data; if ((fd = open(infile,O_RDONLY)) &lt; 0) err(EX_NOINPUT, "%s", infile); if ((data = malloc(bytes_expected)) == NULL) err(EX_OSERR, "data malloc"); bytes_read = read(fd, data, bytes_expected); if (bytes_read != bytes_expected) printf("Read only %d of %d bytes %d\n", \ bytes_read, bytes_expected,EX_DATAERR); /* ... operate on data ... */ printf("\n"); int i=0; int counter=0; char ch=data[0]; char message[512]; Message* newMessage; while(i!=bytes_read) { while(ch!='\n') { message[counter]=ch; i++; counter++; ch =data[i]; } message[counter]='\n'; message[counter+1]='\0'; //--------------------------------------------------- newMessage = (Message*)parser(message); MessageProcess(newMessage,AssetMap); //-------------------------------------------------- //printf("idNUM %e\n",newMessage-&gt;idNum); free(newMessage); i++; counter=0; ch =data[i]; } free(data); } </code></pre> <p>Here, I have allocated 100MB of data with malloc, and passed a file big enough(not 500MB) size of 926KB about. When I pass small files, it reads and exits like a charm, but when I pass a big enough file, the program executes till some point after which it just hangs. I suspect it either entered an infinite loop, or there is memory leak.</p> <p><strong>EDIT</strong> For better understanding I stripped away all unnecessary function calls, and checked what happens, when given a large file as input. I have attached the modified code</p> <pre><code>void ReadBinary(char *infile,HXmap* AssetMap) { int fd; size_t bytes_read, bytes_expected = 500000000*sizeof(char); char *data; if ((fd = open(infile,O_RDONLY)) &lt; 0) err(EX_NOINPUT, "%s", infile); if ((data = malloc(bytes_expected)) == NULL) err(EX_OSERR, "data malloc"); bytes_read = read(fd, data, bytes_expected); if (bytes_read != bytes_expected) printf("Read only %d of %d bytes %d\n", \ bytes_read, bytes_expected,EX_DATAERR); /* ... operate on data ... */ printf("\n"); int i=0; int counter=0; char ch=data[0]; char message[512]; while(i&lt;=bytes_read) { while(ch!='\n') { message[counter]=ch; i++; counter++; ch =data[i]; } message[counter]='\n'; message[counter+1]='\0'; i++; printf("idNUM \n"); counter=0; ch =data[i]; } free(data); } </code></pre> <p>What looks like is, it prints a whole lot of <code>idNUM</code>'s and then <em>poof</em> <code>segmentation fault</code></p> <p>I think this is an interesting behaviour, and to me it looks like there is some problem with memory</p> <p><strong>FURTHER EDIT</strong> I changed back the <code>i!=bytes_read</code> it gives no segmentation fault. When I check for <code>i&lt;=bytes_read</code> it blows past the limits in the innerloop.(courtesy gdb)</p>
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    1. CO`sizeof(char)` is `1`. There is no reason to ever write that in your program.
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      1. USCarl Norum
    2. COYeah, I just kept it for the sake of tomorrow, when I say, I dont want to allocate for a char but for a double.Just saying
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    3. CO@Carl On the hp48 the sizeof(char) was 2 :-) ...units were 4 bits...
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      1. USRing Ø
 

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