Unit test in xcode : inconsistent build result - iphone

Question

Test Case '-[TestParse testParsing]' started.
/Developer/Tools/RunPlatformUnitTests.include: line 415: 3256 Segmentation fault "${THIN_TEST_RIG}" "${OTHER_TEST_FLAGS}" "${TEST_BUNDLE_PATH}"
/Developer/Tools/RunPlatformUnitTests.include:451: error: Test rig '/Developer/Platforms /iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.2.sdk/Developer/usr/bin/otest'
exited abnormally with code 139 (it may have crashed).
I got this seg fault message while I built test case randomly (sometime it built successfully, sometimes it throws seg fault). I'm not sure how I could fix this error.
Only thing I test here is I wrote one class name Parse with class level method. And in test case I just call it like
var = [Parse methodName:filepath];
method is like this
NSMutableDictionary *tempBox = [[NSMutableDictionary alloc] init];
FILE *fd = fopen([filePath UTF8String], "r");
if(!fd){
NSLog(#"fail to open file\n");
}
char buf[4096], *ptr;
char name[512], description[4096];
int isNewInfo = 2, description_continue = 0;
// for (line = 0; line < [args objectAtIndex:1]; line++) {
// fgets(buf, 4096, fd);
// }
while(fgets(buf, sizeof(buf), fd) != NULL){
if(strcmp(buf, "\n") == 0){
isNewInfo -= 1;
if(isNewInfo == 0){
isNewInfo = 2;
description_continue = 0;
description[strlen(description)-1] = '\0';
[self saveDrinkandResetBuf:name
detail:description box:tempBox];
if(name[0] != 0 || description[0] != 0){
NSLog(#"fail to reset...");
}
}
}
if(description_continue){
strcat(description, buf);
continue;
}
if((ptr = strstr(buf, "Drink Name: "))){
memcpy(name, buf+12, strlen(buf));
name[strlen(name)] = '\0';
continue;
}
if((ptr = strstr(buf, "Description: "))){
memcpy(description, buf+13, strlen(buf));
description_continue = 1;
continue;
}
}
fclose(fd);
NSLog(#"finish parsing section\n");
//[tempBox release];
return tempBox;
Not sure what is going on here..

Answer 1

I suppose, the problem is in array management.
In C if the array is declared in a function (and is not declared as a global or static one), then value of its elements is undefined. So your char description[4096] is filled with any values. And nobody said that '\0' will be there.
And the result of strlen(...) for non-null-terminated char string is not defined. It may result in a memory access violation, as it will keep counting until it reaches the first memory byte whose value is 0.
Moreover, when you call description[strlen(description)-1], strlen can return 0 (imagine that the first value, stored there initially was '\0' and your file was started with two empty lines [to reach this line of code]) - so array index will be -1...