Debugging with GDB: Lazy Strings In Guile

Debugging with GDB: Lazy Strings In Guile

23.3.3.20 Guile representation of lazy strings.

A lazy string is a string whose contents is not retrieved or encoded until it is needed.

A <gdb:lazy-string> is represented in GDB as an address that points to a region of memory, an encoding that will be used to encode that region of memory, and a length to delimit the region of memory that represents the string. The difference between a <gdb:lazy-string> and a string wrapped within a <gdb:value> is that a <gdb:lazy-string> will be treated differently by GDB when printing. A <gdb:lazy-string> is retrieved and encoded during printing, while a <gdb:value> wrapping a string is immediately retrieved and encoded on creation.

The following lazy-string-related procedures are provided by the (gdb) module:

Scheme Procedure: lazy-string? object: Return #t if object is an object of type <gdb:lazy-string>. Otherwise return #f.

Scheme Procedure: lazy-string-address lazy-sring: Return the address of lazy-string.

Scheme Procedure: lazy-string-length lazy-string: Return the length of lazy-string in characters. If the length is -1, then the string will be fetched and encoded up to the first null of appropriate width.

Scheme Procedure: lazy-string-encoding lazy-string: Return the encoding that will be applied to lazy-string when the string is printed by GDB. If the encoding is not set, or contains an empty string, then GDB will select the most appropriate encoding when the string is printed.

Scheme Procedure: lazy-string-type lazy-string: Return the type that is represented by lazy-string’s type. For a lazy string this is a pointer or array type. To resolve this to the lazy string’s character type, use type-target-type. See Types In Guile.

Scheme Procedure: lazy-string->value lazy-string: Convert the <gdb:lazy-string> to a <gdb:value>. This value will point to the string in memory, but will lose all the delayed retrieval, encoding and handling that GDB applies to a <gdb:lazy-string>.