Hello Dan,
On Wed, Jun 01, 2005 at 01:45:49PM -0400, Dan Manthey wrote:
> By the way, note that there seems to be some confusion about whether a
> PROG variable is "set". `PROG=' does _not_ unset it. How does
> AC_CHECK_PROG behave when the variable is set to the empty string?
it uses test "x$VAR" = x
Thus the manual should use the term "is nonempty", not "is set".
(One of the reasons for this behaviour is that unset is not portable.)
Another problem of the documentation is that the same pattern is repeated
in the description of each of the macros. I tried to fix this some time
ago, but then I put it ad acta with a note "this patch has to be repaired".
I attach the old patch, for reference. If you or anyone else here could
finish it, I'd be grateful.
Have a nice day,
Stepan Kasal
This patch is not entirely correct.
We should used "is nonempty" instead of "is set".
And it's possible that I'm also missing something else.
2004-10-27 Stepan Kasal <kasal@xxxxxx>
* doc/autoconf.texi (Alternative Programs): Rename the node to ...
(Programs): ... this. Add a general information, ...
(Generic Programs): ... removing it from the description of
individual macros.
(Particular Programs, AC_PROG_GREP): Improve a formulation.
--- doc/autoconf.texi.a2 2004-10-27 11:12:47.000000000 +0200
+++ doc/autoconf.texi 2004-10-27 11:31:27.000000000 +0200
@@ -325,7 +325,7 @@
Existing Tests
* Common Behavior:: Macros' standard schemes
-* Alternative Programs:: Selecting between alternative programs
+* Programs:: Selecting between alternative programs
* Files:: Checking for the existence of files
* Libraries:: Library archives that might be missing
* Library Functions:: C library functions that might be missing
@@ -342,7 +342,7 @@
* Standard Symbols:: Symbols defined by the macros
* Default Includes:: Includes used by the generic macros
-Alternative Programs
+Programs
* Particular Programs:: Special handling to find certain programs
* Generic Programs:: How to find other programs
@@ -3078,7 +3078,7 @@
@menu
* Common Behavior:: Macros' standard schemes
-* Alternative Programs:: Selecting between alternative programs
+* Programs:: Selecting between alternative programs
* Files:: Checking for the existence of files
* Libraries:: Library archives that might be missing
* Library Functions:: C library functions that might be missing
@@ -3212,16 +3212,38 @@
@code{HAVE_STRINGS_H} won't.
@end defmac
-@node Alternative Programs
-@section Alternative Programs
+@node Programs
+@section Programs
@cindex Programs, checking
These macros check for the presence or behavior of particular programs.
-They are used to choose between several alternative programs and to
-decide what to do once one has been chosen. If there is no macro
-specifically defined to check for a program you need, and you don't need
-to check for any special properties of it, then you can use one of the
-general program-check macros.
+They are also used to choose between several alternative programs and to
+decide what to do once one has been chosen.
+
+If there is no macro specifically defined to check for a program you
+need, and you don't need to check for any special properties of it, then
+you can use one of the general program-check macros.
+
+These macros work with an environment variable, eg.@ @code{GREP}; for
+the generic macros, you specify the variable name as the first
+parameter.
+
+If the variable is already set, the macro does nothing.
+
+If it is not set, it looks for the program. If the program is found,
+it's name is assigned to the variable. (Or name with parameters, or
+full pathname, it depends on the individual macros.) If the program is
+not found and the optional parameter @var{value-if-not-found} was
+specified, that value is assigned to the variable.
+
+All these macros call AC_SUBST on the variable.
+
+As the result depends on the initial value of the variable, it should
+be declared as precious. This is done automatically by the specific
+tests. For the generic macros, you are strongly encouradged to declare
+the variable as precious, @xref{Setting Output Variables},
+@code{AC_ARG_VAR}, for more details. (Another possibility would be
+to unset the variable before calling the macro.)
@menu
* Particular Programs:: Special handling to find certain programs
@@ -3252,8 +3274,8 @@
single @option{-e} option. This macro looks for @sc{gnu} Grep or
else the best available @code{grep} or @code{ggrep} in the user's
@code{$PATH} which accepts the longest input lines possible, and which
-accepts and respects multiple @option{-e} options. Set the
-output variable @code{GREP} to whatever is chosen.
+accepts and respects multiple @option{-e} options. It sets the output
+variable @code{GREP} to whatever is chosen.
@end defmac
@defmac AC_PROG_EGREP
@@ -3433,9 +3455,7 @@
@var{value-if-not-found}, if given. Always pass over @var{reject} (an
absolute file name) even if it is the first found in the search path; in
that case, set @var{variable} using the absolute file name of the
-@var{prog-to-check-for} found that is not @var{reject}. If
-@var{variable} was already set, do nothing. Calls @code{AC_SUBST} for
-@var{variable}.
+@var{prog-to-check-for} found that is not @var{reject}.
@end defmac
@defmac AC_CHECK_PROGS (@var{variable}, @var{progs-to-check-for}, @ovar{value-if-not-found}, @ovar{path})
@@ -3444,9 +3464,8 @@
@var{progs-to-check-for} existing in the @env{PATH}. If one is found, set
@var{variable} to the name of that program. Otherwise, continue
checking the next program in the list. If none of the programs in the
-list are found, set @var{variable} to @var{value-if-not-found}; if
-@var{value-if-not-found} is not specified, the value of @var{variable}
-is not changed. Calls @code{AC_SUBST} for @var{variable}.
+list are found, set @var{variable} to @var{value-if-not-found} (if it is
+specified).
@end defmac
@defmac AC_CHECK_TARGET_TOOL (@var{variable}, @var{prog-to-check-for}, @ovar{value-if-not-found}, @ovar{path})
@@ -3496,9 +3515,7 @@
prefix, and if the build and target types are equal, then the first one
without a prefix is used. If a tool is found, set @var{variable} to
the name of that program. If none of the tools in the list are found,
-set @var{variable} to @var{value-if-not-found}; if @var{value-if-not-found}
-is not specified, the value of @var{variable} is not changed. Calls
-@code{AC_SUBST} for @var{variable}.
+set @var{variable} to @var{value-if-not-found}, if it is given.
@end defmac
@defmac AC_CHECK_TOOLS (@var{variable}, @var{progs-to-check-for}, @ovar{value-if-not-found}, @ovar{path})
@@ -3509,9 +3526,8 @@
(@pxref{Canonicalizing}). If none of the tools can be found with a
prefix, then the first one without a prefix is used. If a tool is found,
set @var{variable} to the name of that program. If none of the tools in
-the list are found, set @var{variable} to @var{value-if-not-found}; if
-@var{value-if-not-found} is not specified, the value of @var{variable}
-is not changed. Calls @code{AC_SUBST} for @var{variable}.
+the list are found, set @var{variable} to @var{value-if-not-found}, if
+specified.
In the future, when cross-compiling this macro will @emph{not}
accept program names that are not prefixed with the host type.
_______________________________________________
Autoconf mailing list
Autoconf@xxxxxxx
http://lists.gnu.org/mailman/listinfo/autoconf
