iOS error read memory failed - ios

Question

I'm working on an iPad app.
When the app is launched, user have to enter a number. With this id, I check in a csv file to get informations about the user.
Informations are saved with a singleton. This singleton is causing me problems :
step 1 : initialization of my singleton
+(ASMagasin*) sharedInstance {
if (myMagasin == nil){
myMagasin = [[ASMagasin alloc]init];
}
return myMagasin;
}
step 2 : I call my function which work with the csv file
- (id)init {
if (self = [super init]) {
NSError * error;
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString * num_magasin = [defaults objectForKey:kUserDefautNumMagasin];
[self loadMagFromCsv:filePathCsv withMagasin:num_magasin];
}
return self;
}
step 3 :
-(void)loadMagFromCsv:(NSString *)filePath withMagasin:(NSString *) num_magasin
{
NSError *error;
NSString *csvData = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
NSArray *gcRawData = [csvData componentsSeparatedByString:#"\n"];
NSArray *singleGC = [NSArray array];
for (int i = 0; i < gcRawData.count; i++)
{
NSString *nextGCString = [NSString stringWithFormat:#"%#", gcRawData[i]];
singleGC = [nextGCString componentsSeparatedByString:#","];
if ([singleGC[0]isEqualToString:num_magasin]){
_num=singleGC[0];
_libelle=singleGC[1];
_client_defaut_nom=singleGC[2];
_client_defaut_prenom=singleGC[3];
_client_defaut_tel=singleGC[4];
_client_defaut_mail=singleGC[5];
_cp=singleGC[6];
_ville=singleGC[7];
_pays=singleGC[8];
}
}
}
In this function, my variable error have this value before I initialize it :
(NSError *) error = 0x0000000000000001 domain: read memory from 0x19
failed (0 of 8 bytes read) - code: read memory from 0x11 failed (0 of
8 bytes read)
I don't know how to solve that and where is this error come from.

Answer 1

You are looking at random memory in the heap. It is meaningless. Your NSError hasn't even been initialised at this point, let alone assigned a value.
You can (and should) check error for a value after you execute the line
NSString *csvData = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
Before that error doesn't have a useful value.

Answer 2

I am posting it with a hope that it might help others facing same issue. Not sure about its exact cause, but I was experiencing it on a variable with _block before it. Removing _block fixed this issue and didn't give any warning either. Not sure what is going on here as I experienced it after updating to iOS 14. Will update if i find anything more interesting.