mingw/info/gdb/C-Constants.html

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  12 Node:<a name="C%20Constants">C Constants</a>,
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  19 <h5 class="subsubsection">C and C<tt>++</tt> constants</h5>
  20
  21    GDB allows you to express the constants of C and C<tt>++</tt> in the
  22 following ways:
  23
  24      <ul>
  25 <li>Integer constants are a sequence of digits.  Octal constants are
  26 specified by a leading <code>0</code> (i.e. zero), and hexadecimal constants
  27 by a leading <code>0x</code> or <code>0X</code>.  Constants may also end with a letter
  28 <code>l</code>, specifying that the constant should be treated as a
  29 <code>long</code> value.
  30
  31      <li>Floating point constants are a sequence of digits, followed by a decimal
  32 point, followed by a sequence of digits, and optionally followed by an
  33 exponent.  An exponent is of the form:
  34 <code>e</code>[[<code>+</code>]|<code>-</code>]<code></code><var>nnn</var><code></code>, where <var>nnn</var> is another
  35 sequence of digits.  The <code>+</code> is optional for positive exponents.
  36 A floating-point constant may also end with a letter <code>f</code> or
  37 <code>F</code>, specifying that the constant should be treated as being of
  38 the <code>float</code> (as opposed to the default <code>double</code>) type; or with
  39 a letter <code>l</code> or <code>L</code>, which specifies a <code>long double</code>
  40 constant.
  41
  42      <li>Enumerated constants consist of enumerated identifiers, or their
  43 integral equivalents.
  44
  45      <li>Character constants are a single character surrounded by single quotes
  46 (<code>'</code>), or a number--the ordinal value of the corresponding character
  47 (usually its <small>ASCII</small> value).  Within quotes, the single character may
  48 be represented by a letter or by <dfn>escape sequences</dfn>, which are of
  49 the form <code>\</code><var>nnn</var><code></code>, where <var>nnn</var> is the octal representation
  50 of the character's ordinal value; or of the form <code>\</code><var>x</var><code></code>, where
  51 <code></code><var>x</var><code></code> is a predefined special character--for example,
  52 <code>\n</code> for newline.
  53
  54      <li>String constants are a sequence of character constants surrounded by
  55 double quotes (<code>"</code>).  Any valid character constant (as described
  56 above) may appear.  Double quotes within the string must be preceded by
  57 a backslash, so for instance <code>"a\"b'c"</code> is a string of five
  58 characters.
  59
  60      <li>Pointer constants are an integral value.  You can also write pointers
  61 to constants using the C operator <code>&amp;</code>.
  62
  63      <li>Array constants are comma-separated lists surrounded by braces <code>{</code>
  64 and <code>}</code>; for example, <code>{1,2,3}</code> is a three-element array of
  65 integers, <code>{{1,2}, {3,4}, {5,6}}</code> is a three-by-two array,
  66 and <code>{&amp;"hi", &amp;"there", &amp;"fred"}</code> is a three-element array of pointers.
  67 </ul>
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