Enums less than 32 bit?

Question

Hi!
I tried to compile LyX with Sun Studio 12u1 on snv_132. I came accross this error:
Error: lyx::Debug::Type is not within the range of a long or unsigned long.
The source is:
     enum Type {
          NONE = 0,
          INFO = (1 << 0), // 1
          INIT = (1 << 1), // 2
          KEY = (1 << 2), // 4
          GUI = (1 << 3), // 8
          PARSER = (1 << 4), // 16
          LYXRC = (1 << 5), // 32
          KBMAP = (1 << 6), // 64
          LATEX = (1 << 7), // 128
          MATHED = (1 << 8), // 256 // Alejandro, please use this.
          FONT = (1 << 9), // 512
          TCLASS = (1 << 10), // 1024
          LYXVC = (1 << 11), // 2048
          LYXSERVER = (1 << 12), // 4096
          UNDO = (1 << 13), // 8192
          ACTION = (1 << 14), // 16384
          LYXLEX = (1 << 15),
          DEPEND = (1 << 16),
          INSETS = (1 << 17),
          FILES = (1 << 18),
          WORKAREA = (1 << 19),
          INSETTEXT = (1 << 20),
          GRAPHICS = (1 << 21),
          /// change tracking
          CHANGES = (1 << 22),
          EXTERNAL = (1 << 23),
          PAINTING = (1 << 24),
          SCROLLING = (1 << 25),
          MACROS = (1 << 26),
          ///     rtl-related
          RTL = (1 << 27),
          ///     locale related
          LOCALE = (1 << 28),
          ///     selection
          SELECTION = (1 << 29),
          DEBUG = (1 << 31),
          ANY = 0xffffffff
When I change the DEBUG to (1 << 30) it compiles without problems.
Why is that so?

Answer 1

(1 << 31) is a negative number; it makes enum values to span from -INT_MAX (lowest possible value for int) to UINT_MAX (highest possible value for unsigned int).
Naturally, it doesn't fit in type long (assuming 32-bit compilation) because of ANY constant as well as unsigned long because of DEBUG, which is negative.
When you change (1<<31) to (1u<<31), its type becomes unsigned and value large positive integer. Consequently, it allows enum to fit in with unsigned long.