Pitfall: Release Scheme Optimizes Code
I was once writing a simple piece of code, something along the line of:
NSString *name = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleDisplayName"];
It turns out strange that when I run in Release scheme, name is
nil when I inspect the variable in debugger.
When I run in Debug scheme, it is fine. The code returns the app name as you expected.
The pitfall is that when you run in Release mode, the code is optimized.
The effect of the optimization is such that any information you see in debugger could not be the truth.
It might not be
nil, though you see
nil in debugger.
If you were to print out the variable at that breakpoint with lldb, it could say:
Printing description of name: (NSString *) name = <no location, value may have been optimized out>
Printing description of name: (NSString *) name = <variable not available>
Both does not give you the true value of name. But at least they don’t wrongly says the variable is
It you really want to debug in Release mode, you can change the optimzation level.
Go to Project > App target > Build Settings > Optimization Level and change to
None for Release.
But remember to change it back for actual app release.