Re: [Xen-devel] [PATCH v4 2/2] xl: Add commands for usb hot-plug

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [Xen-devel] [PATCH v4 2/2] xl: Add commands for usb 
hot-plug"):
> On Wed, 2013-04-17 at 11:02 +0100, Roger Pau Monné wrote:
> > This are kind of general macros, that could be used elsewhere, might be
> > suitable to put them outside of this function and name them CHAR_IS_DEC
> > and CHAR_IS_HEX.
> 
> ctype.h already provides isdigit() and isxdigit(), no need for our own.
> IMHO.

These functions' behaviour depends on the locale.  That may or may not
be desirable.

If you do use isdigit, be sure to invoke it via the CTYPE macro in
libxl_internal.h:

  /*
   * int CTYPE(ISFOO, char c);
   * int CTYPE(toupper, char c);
   * int CTYPE(tolower, char c);
   *
   * This is necessary because passing a simple char to a ctype.h
   * is forbidden.  ctype.h macros take ints derived from _unsigned_ chars.
   *
   * If you have a char which might be EOF then you should already have
   * it in an int representing an unsigned char, and you can use the
   * <ctype.h> macros directly.  This generally happens only with values
   * from fgetc et al.
   *
   * For any value known to be a character (eg, anything that came from
   * a char[]), use CTYPE.
   */
  #define CTYPE(isfoo,c) (isfoo((unsigned char)(c)))

Ian.

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