I stumbled onto:
atoi("v10") == 10
The repository shows the assembler version of atoi is correct but my version of avr-libc incorrectly checks the string for 'v' instead of '\v' (vertical tab 0xb).
Sorry if this is a known problem but my searching did not reveal anything.
I thought atoi() converted digits until it found the first non-numeric. As such I'd have thought atoi("v10") should be 0 as the conversion should terminate on the first character??
I don't have my reference books handy to check this. But if it returns 10 then it sounds like something might be wrong.
Cliff
EDIT: this: http://www.cplusplus.com/referen... and specifically "If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed" seems to confirm my understanding
atoi("v10") should be zero but returns 10 for me.
Also, atoi("\v10") should return 10 but returns zero for me.
Well this is curious. The code that performs atoi() does this (amongst other things):
+0000005C: 9121 LD R18,Z+ +0000005D: 2322 TST R18 +0000005E: F0F1 BREQ PC+0x1F +0000005F: 3220 CPI R18,0x20 +00000060: F3D9 BREQ PC-0x04 +00000061: 3029 CPI R18,0x09 +00000062: F3C9 BREQ PC-0x06 +00000063: 302A CPI R18,0x0A +00000064: F3B9 BREQ PC-0x08 +00000065: 302C CPI R18,0x0C +00000066: F3A9 BREQ PC-0x0A +00000067: 302D CPI R18,0x0D +00000068: F399 BREQ PC-0x0C +00000069: 3726 CPI R18,0x76 +0000006A: F389 BREQ PC-0x0E +0000006B: 322B CPI R18,0x2B +0000006C: F019 BREQ PC+0x04 +0000006D: 322D CPI R18,0x2D +0000006E: F421 BRNE PC+0x05
It's comparing characters in the string against all the "usual suspects" such as space, tab, line feed etc but notice that compare with 0x76 - it's specifically looking for a lower case 'v' and treating it as the other "white space" characters??
Cliff
Since the assembler source I saw correctly performs the comparison on \v then it seems likely that there is either a problem with the assembler itself or a different source file was used.
The vertical tab character is probably pretty unusual so missing that whitespace is not a huge deal. But counting the lower case v as whitespace might be more problematic.
Further, if the assembler has a problem then this incorrect behavior may be present in other routines and libraries.
atol appears to have the same problem:
PUSH r17 MOVW r30,r24 EOR r25,r25 EOR r24,r24 EOR r23,r23 EOR r22,r22 BCLR 6 LD r17, Z+ TST r17 BREQ 32 CPI r17, 0x20 BREQ -4 CPI r17, 0x9 BREQ -6 CPI r17, 0xa BREQ -8 CPI r17, 0xc BREQ -10 CPI r17, 0xd BREQ -12 CPI r17, 0x76
An assembler anomaly I guess.
This is not a problem with the assembler but with the code itself.
There is no known escape sequence for '\v' for the assembler.
Please file a bug report with the avr-libc project.
AFAICT only atoi.S and atol.S are affected. The code in ctype.S
explicitly uses hexadecimal numbers rather than escape characters.
