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Strange C string and NSString comparison problem

Pay attention to the following code:

NSString *string = @"ä";
const char *str1 = [string cStringUsingEncoding:NSUTF8StringEncoding];
const char *str2 = "ä";
NSLog(@"C string comparison: %d",strcmp(str1,str2));
NSLog(@"str1: \"%s\"", str1);
NSLog(@"str2: \"%s\"", str2);

When launched from a completely new Foundation project, this program outputs:

C string comparison: 0
str1: "ä"
str2: "ä"

This is really what I expect, because the lines should be the same.

However, if I run this exact code somewhere deep in a different code base, I get this output:

C string comparison: 31
str1: "ä"
str2: "ä"

What can explain this difference? I am sure that both files are in UTF-8 encoding. These are different file encodings - the only possible explanation for this behavior, right?

Any ideas what could go wrong in the second case? How can i fix this?

(Perhaps it is worth mentioning that in the second case, the code runs in a file .mm, i.e. under Objective-C ++. Could this be an explanation for this?)

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I think that in your case either the recipient is freed or the current pool of auto resources is empty.
for instance

NSString *string = @"ä";
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
const char *str3 = [string cStringUsingEncoding:NSUTF8StringEncoding];
[pool release];
NSLog(@"str1: \"%s\"", str3);
const char *str2 = "ä";
NSLog(@"C string comparison: %d",strcmp(str3,str2));
NSLog(@"str2: \"%s\"", str2);

Output

2012-05-22 17:14:50.069 test[32895:a0f] str1: "ä"
2012-05-22 17:14:50.071 test[32895:a0f] C string comparison: -195
2012-05-22 17:14:50.074 test[32895:a0f] str2: "ä" 



NSString *string = @"ä";
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
const char *str3 = [string cStringUsingEncoding:NSUTF8StringEncoding];
[pool release];
const char *str2 = "ä";
NSLog(@"C string comparison: %d",strcmp(str3,str2));
NSLog(@"str1: \"%s\"", str3);
NSLog(@"str2: \"%s\"", str2);

Output

2012-05-22 17:19:13.226 test[33153:a0f] C string comparison: 0
2012-05-22 17:19:13.228 test[33153:a0f] str1: ""
2012-05-22 17:19:13.229 test[33153:a0f] str2: "ä"
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