Different values compiling for what I believe should be the same code

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Steve Tulk

• May 02, 2018 09:33

I ran across a very strange issue with how numbers are interpreted using #define with and without a leading zero. 

See the 2 below examples and the comment I put next to each:

#define LED_DRIVER_BOARD_TYPE 0270 // This compiles as 0x00B8 which is not correct

#define LED_DRIVER_BOARD_TYPE 270 // This compiles as 0x010E, which is correct

Why would these not be the same number? I tried this in version 3.7.7 and 4.1.0 and they both the same. Is this a compiler bug I stumbled on or is this something with C that I am not aware of?

Thanks

Steve

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  Steve Tulk

  • May 02, 2018 09:34

  Forgot to add. Both Crossworks tried were Linux versions

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  Jon Elliott

  • May 02, 2018 09:40

  This is correct behaviour, a leading zero indicates an octal literal in C/C++ ( http://en.cppreference.com/w/cpp/language/integer_literal ).

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  Steve Tulk

  • May 02, 2018 09:56

  Thank You for clearing that up!! I guess I should have realized that as I have come across 08 and 09 giving the error of Illegal Octal number and have had to code around that one for years. 

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