-C implementations differ substantially. Standard C reduces but does
-not eliminate the incompatibilities; meanwhile, many GNU packages still
-support pre-standard compilers because this is not hard to do. This
-chapter gives recommendations for how to use the more-or-less standard C
-library functions to avoid unnecessary loss of portability.
-
-@itemize @bullet
-@item
-Don't use the return value of @code{sprintf}. It returns the number of
-characters written on some systems, but not on all systems.
-
-@item
-Be aware that @code{vfprintf} is not always available.
-
-@item
-@code{main} should be declared to return type @code{int}. It should
-terminate either by calling @code{exit} or by returning the integer
-status code; make sure it cannot ever return an undefined value.
-
-@cindex declaration for system functions
-@item
-Don't declare system functions explicitly.
-
-Almost any declaration for a system function is wrong on some system.
-To minimize conflicts, leave it to the system header files to declare
-system functions. If the headers don't declare a function, let it
-remain undeclared.
-
-While it may seem unclean to use a function without declaring it, in
-practice this works fine for most system library functions on the
-systems where this really happens; thus, the disadvantage is only
-theoretical. By contrast, actual declarations have frequently caused
-actual conflicts.
-
-@item
-If you must declare a system function, don't specify the argument types.
-Use an old-style declaration, not a Standard C prototype. The more you
-specify about the function, the more likely a conflict.
-
-@item
-In particular, don't unconditionally declare @code{malloc} or
-@code{realloc}.
-
-Most GNU programs use those functions just once, in functions
-conventionally named @code{xmalloc} and @code{xrealloc}. These
-functions call @code{malloc} and @code{realloc}, respectively, and
-check the results.
-
-Because @code{xmalloc} and @code{xrealloc} are defined in your program,
-you can declare them in other files without any risk of type conflict.
-
-On most systems, @code{int} is the same length as a pointer; thus, the
-calls to @code{malloc} and @code{realloc} work fine. For the few
-exceptional systems (mostly 64-bit machines), you can use
-@strong{conditionalized} declarations of @code{malloc} and
-@code{realloc}---or put these declarations in configuration files
-specific to those systems.
-
-@cindex string library functions
-@item
-The string functions require special treatment. Some Unix systems have
-a header file @file{string.h}; others have @file{strings.h}. Neither
-file name is portable. There are two things you can do: use Autoconf to
-figure out which file to include, or don't include either file.
-
-@item
-If you don't include either strings file, you can't get declarations for
-the string functions from the header file in the usual way.
-
-That causes less of a problem than you might think. The newer standard
-string functions should be avoided anyway because many systems still
-don't support them. The string functions you can use are these: