15.4.1.2 C and C++ Constants

gdb allows you to express the constants of C and C++ in the following ways:

• Integer constants are a sequence of digits. Octal constants are specified by a leading `0' (i.e. zero), and hexadecimal constants by a leading `0x' or `0X'. Constants may also end with a letter `l', specifying that the constant should be treated as a long value.
• Floating point constants are a sequence of digits, followed by a decimal point, followed by a sequence of digits, and optionally followed by an exponent. An exponent is of the form: `e[[+]|-]nnn', where nnn is another sequence of digits. The `+' is optional for positive exponents. A floating-point constant may also end with a letter `f' or `F', specifying that the constant should be treated as being of the float (as opposed to the default double) type; or with a letter `l' or `L', which specifies a long double constant.
• Enumerated constants consist of enumerated identifiers, or their integral equivalents.
• Character constants are a single character surrounded by single quotes ('), or a number—the ordinal value of the corresponding character (usually its ascii value). Within quotes, the single character may be represented by a letter or by escape sequences, which are of the form `\nnn', where nnn is the octal representation of the character's ordinal value; or of the form `\x', where `x' is a predefined special character—for example, `\n' for newline.

  Wide character constants can be written by prefixing a character constant with `L', as in C. For example, `L'x'' is the wide form of `x'. The target wide character set is used when computing the value of this constant (see Character Sets).

• String constants are a sequence of character constants surrounded by double quotes ("). Any valid character constant (as described above) may appear. Double quotes within the string must be preceded by a backslash, so for instance `"a\"b'c"' is a string of five characters.

  Wide string constants can be written by prefixing a string constant with `L', as in C. The target wide character set is used when computing the value of this constant (see Character Sets).

• Pointer constants are an integral value. You can also write pointers to constants using the C operator `&'.
• Array constants are comma-separated lists surrounded by braces `{' and `}'; for example, `{1,2,3}' is a three-element array of integers, `{{1,2}, {3,4}, {5,6}}' is a three-by-two array, and `{&"hi", &"there", &"fred"}' is a three-element array of pointers.