ios - Strange behaviours with stringWithFormat float - 


(lldb) po [nsstring stringwithformat:@"%.1f", 0.01] (id) $21 = 0x003a2560 19991592471028323832250853378750414848.0 (lldb) po [nsstring stringwithformat:@"%.1f", 0.1] (id) $22 = 0x0de92240 -0.0

does understand behaviour here? i'm running on device.

it's bug in lldb. if try same thing in gdb, works properly. suspect lldb passing low 32 bits of argument. ieee representation of 0.01 , of number it's printing these:

47ae147b3778df69 = 19991592471028323832250853378750414848.00 3f847ae147ae147b = 0.01

notice low 32 bits of 0.01 match high 32 bits of other number.

the bug happens printf:

(lldb) expr (void)printf("%.1f\n", 0.01) 19991592257096858016910903319197646848.0 <no result>

it doesn't happen +[nsnumber numberwithdouble:]:

(lldb) po [nsnumber numberwithdouble:0.01] (id) $3 = 0x0fe81390 0.01

so suspect bug in lldb's handling of variadic functions.

you can open bug report @ the llvm bugzilla and/or @ apple's bug reporter (aka rdar).


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