-Given three strings @var{progname}, @var{bin_prefix}, @var{prefix}, return a string
-that gets to @var{prefix} starting with the directory portion of @var{progname} and
-a relative pathname of the difference between @var{bin_prefix} and @var{prefix}.
-
-For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta}, @var{prefix}
-is @code{/alpha/beta/gamma/omega/}, and @var{progname} is @code{/red/green/blue/gcc},
-then this function will return @code{/red/green/blue/../../omega/}.
-
-The return value is normally allocated via @code{malloc}. If no relative prefix
-can be found, return @code{NULL}.
+Given three paths @var{progname}, @var{bin_prefix}, @var{prefix},
+return the path that is in the same position relative to
+@var{progname}'s directory as @var{prefix} is relative to
+@var{bin_prefix}. That is, a string starting with the directory
+portion of @var{progname}, followed by a relative pathname of the
+difference between @var{bin_prefix} and @var{prefix}.
+
+If @var{progname} does not contain any directory separators,
+@code{make_relative_prefix} will search @env{PATH} to find a program
+named @var{progname}. Also, if @var{progname} is a symbolic link,
+the symbolic link will be resolved.
+
+For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta},
+@var{prefix} is @code{/alpha/beta/gamma/omega/}, and @var{progname} is
+@code{/red/green/blue/gcc}, then this function will return
+@code{/red/green/blue/../../omega/}.
+
+The return value is normally allocated via @code{malloc}. If no
+relative prefix can be found, return @code{NULL}.