[PATCH] cvexpr.c: Don't let linker delete unused globals

[PATCH] cvexpr.c: Don't let linker delete unused globals

[Kevin Buettner]

On AIX, I was seeing lots of failures in gdb.base/code-expr.exp and
gdb.base/cvexpr.exp due to the fact that the linker deletes unused
symbols.  The patch below fixes these failures.

Committed as obvious.

	* gdb.base/cvexpr.c (use): New function.
	(main): Invoke use() on all global variables to prevent
	some linkers from deleting these otherwise unused symbols.

Index: cvexpr.c
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/cvexpr.c,v
retrieving revision 1.1
diff -u -p -r1.1 cvexpr.c
--- cvexpr.c	15 Nov 2001 02:16:59 -0000	1.1
+++ cvexpr.c	18 Apr 2002 12:59:53 -0000
@@ -273,8 +273,162 @@ unsigned long long	(*v_unsigned_long_lon
 float		(*v_float_func) (int, int*);
 double		(*v_double_func) (int, int*);
 
-
+void use (void *p)
+{
+}
 
 int main ()
 {
+  use (&v_char);
+  use (&v_signed_char);
+  use (&v_unsigned_char);
+
+  use (&v_short);
+  use (&v_signed_short);
+  use (&v_unsigned_short);
+
+  use (&v_int);
+  use (&v_signed_int);
+  use (&v_unsigned_int);
+
+  use (&v_long);
+  use (&v_signed_long);
+  use (&v_unsigned_long);
+
+  use (&v_long_long);
+  use (&v_signed_long_long);
+  use (&v_unsigned_long_long);
+
+  use (&v_float);
+  use (&v_double);
+
+  use (v_char_array);
+  use (v_signed_char_array);
+  use (v_unsigned_char_array);
+
+  use (v_short_array);
+  use (v_signed_short_array);
+  use (v_unsigned_short_array);
+
+  use (v_int_array);
+  use (v_signed_int_array);
+  use (v_unsigned_int_array);
+
+  use (v_long_array);
+  use (v_signed_long_array);
+  use (v_unsigned_long_array);
+
+  use (v_float_array);
+  use (v_double_array);
+
+  use (v_char_pointer);
+  use (v_signed_char_pointer);
+  use (v_unsigned_char_pointer);
+
+  use (v_short_pointer);
+  use (v_signed_short_pointer);
+  use (v_unsigned_short_pointer);
+
+  use (v_int_pointer);
+  use (v_signed_int_pointer);
+  use (v_unsigned_int_pointer);
+
+  use (v_long_pointer);
+  use (v_signed_long_pointer);
+  use (v_unsigned_long_pointer);
+
+  use (v_float_pointer);
+  use (v_double_pointer);
+
+  use (v_char_pointer_pointer);
+  use (v_signed_char_pointer_pointer);
+  use (v_unsigned_char_pointer_pointer);
+
+  use (v_short_pointer_pointer);
+  use (v_signed_short_pointer_pointer);
+  use (v_unsigned_short_pointer_pointer);
+
+  use (v_int_pointer_pointer);
+  use (v_signed_int_pointer_pointer);
+  use (v_unsigned_int_pointer_pointer);
+
+  use (v_long_pointer_pointer);
+  use (v_signed_long_pointer_pointer);
+  use (v_unsigned_long_pointer_pointer);
+
+  use (v_float_pointer_pointer);
+  use (v_double_pointer_pointer);
+
+  use (v_char_array_pointer);
+  use (v_signed_char_array_pointer);
+  use (v_unsigned_char_array_pointer);
+
+  use (v_short_array_pointer);
+  use (v_signed_short_array_pointer);
+  use (v_unsigned_short_array_pointer);
+
+  use (v_int_array_pointer);
+  use (v_signed_int_array_pointer);
+  use (v_unsigned_int_array_pointer);
+
+  use (v_long_array_pointer);
+  use (v_signed_long_array_pointer);
+  use (v_unsigned_long_array_pointer);
+
+  use (v_float_array_pointer);
+  use (v_double_array_pointer);
+
+  use (v_char_pointer_array);
+  use (v_signed_char_pointer_array);
+  use (v_unsigned_char_pointer_array);
+
+  use (v_short_pointer_array);
+  use (v_signed_short_pointer_array);
+  use (v_unsigned_short_pointer_array);
+
+  use (v_int_pointer_array);
+  use (v_signed_int_pointer_array);
+  use (v_unsigned_int_pointer_array);
+
+  use (v_long_pointer_array);
+  use (v_signed_long_pointer_array);
+  use (v_unsigned_long_pointer_array);
+
+  use (v_float_pointer_array);
+  use (v_double_pointer_array);
+
+  use (&v_struct1);
+  use (&v_struct2);
+  use (&v_struct3);
+
+  use (&v_union);
+  use (&v_union2);
+  use (&v_union3);
+
+  use (&v_boolean);
+  use (&v_boolean2);
+  use (&v_misordered);
+
+  use (v_char_func);
+  use (v_signed_char_func);
+  use (v_unsigned_char_func);
+
+  use (v_short_func);
+  use (v_signed_short_func);
+  use (v_unsigned_short_func);
+
+  use (v_int_func);
+  use (v_signed_int_func);
+  use (v_unsigned_int_func);
+
+  use (v_long_func);
+  use (v_signed_long_func);
+  use (v_unsigned_long_func);
+
+  use (v_long_long_func);
+  use (v_signed_long_long_func);
+  use (v_unsigned_long_long_func);
+
+  use (v_float_func);
+  use (v_double_func);
 }

Re: [PATCH] cvexpr.c: Don't let linker delete unused globals

[Michael Snyder]

Kevin Buettner wrote:
> 
> On AIX, I was seeing lots of failures in gdb.base/code-expr.exp and
> gdb.base/cvexpr.exp due to the fact that the linker deletes unused
> symbols.  The patch below fixes these failures.
> 
> Committed as obvious.

Wow, that's really sad, to have to add all that code
for such a trivial reason.  I'm sure there are other 
tests in gdb.base that also make use of symbols that
don't get called.  Isn't there some option that you can
give to the linker to tell it not to remove these?

> 
>         * gdb.base/cvexpr.c (use): New function.
>         (main): Invoke use() on all global variables to prevent
>         some linkers from deleting these otherwise unused symbols.
> 
> Index: cvexpr.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/testsuite/gdb.base/cvexpr.c,v
> retrieving revision 1.1
> diff -u -p -r1.1 cvexpr.c
> --- cvexpr.c    15 Nov 2001 02:16:59 -0000      1.1
> +++ cvexpr.c    18 Apr 2002 12:59:53 -0000
> @@ -273,8 +273,162 @@ unsigned long long        (*v_unsigned_long_lon
>  float          (*v_float_func) (int, int*);
>  double         (*v_double_func) (int, int*);
> 
> -
> +void use (void *p)
> +{
> +}
> 
>  int main ()
>  {
> +  use (&v_char);
> +  use (&v_signed_char);
> +  use (&v_unsigned_char);
> +
> +  use (&v_short);
> +  use (&v_signed_short);
> +  use (&v_unsigned_short);
> +
> +  use (&v_int);
> +  use (&v_signed_int);
> +  use (&v_unsigned_int);
> +
> +  use (&v_long);
> +  use (&v_signed_long);
> +  use (&v_unsigned_long);
> +
> +  use (&v_long_long);
> +  use (&v_signed_long_long);
> +  use (&v_unsigned_long_long);
> +
> +  use (&v_float);
> +  use (&v_double);
> +
> +  use (v_char_array);
> +  use (v_signed_char_array);
> +  use (v_unsigned_char_array);
> +
> +  use (v_short_array);
> +  use (v_signed_short_array);
> +  use (v_unsigned_short_array);
> +
> +  use (v_int_array);
> +  use (v_signed_int_array);
> +  use (v_unsigned_int_array);
> +
> +  use (v_long_array);
> +  use (v_signed_long_array);
> +  use (v_unsigned_long_array);
> +
> +  use (v_float_array);
> +  use (v_double_array);
> +
> +  use (v_char_pointer);
> +  use (v_signed_char_pointer);
> +  use (v_unsigned_char_pointer);
> +
> +  use (v_short_pointer);
> +  use (v_signed_short_pointer);
> +  use (v_unsigned_short_pointer);
> +
> +  use (v_int_pointer);
> +  use (v_signed_int_pointer);
> +  use (v_unsigned_int_pointer);
> +
> +  use (v_long_pointer);
> +  use (v_signed_long_pointer);
> +  use (v_unsigned_long_pointer);
> +
> +  use (v_float_pointer);
> +  use (v_double_pointer);
> +
> +  use (v_char_pointer_pointer);
> +  use (v_signed_char_pointer_pointer);
> +  use (v_unsigned_char_pointer_pointer);
> +
> +  use (v_short_pointer_pointer);
> +  use (v_signed_short_pointer_pointer);
> +  use (v_unsigned_short_pointer_pointer);
> +
> +  use (v_int_pointer_pointer);
> +  use (v_signed_int_pointer_pointer);
> +  use (v_unsigned_int_pointer_pointer);
> +
> +  use (v_long_pointer_pointer);
> +  use (v_signed_long_pointer_pointer);
> +  use (v_unsigned_long_pointer_pointer);
> +
> +  use (v_float_pointer_pointer);
> +  use (v_double_pointer_pointer);
> +
> +  use (v_char_array_pointer);
> +  use (v_signed_char_array_pointer);
> +  use (v_unsigned_char_array_pointer);
> +
> +  use (v_short_array_pointer);
> +  use (v_signed_short_array_pointer);
> +  use (v_unsigned_short_array_pointer);
> +
> +  use (v_int_array_pointer);
> +  use (v_signed_int_array_pointer);
> +  use (v_unsigned_int_array_pointer);
> +
> +  use (v_long_array_pointer);
> +  use (v_signed_long_array_pointer);
> +  use (v_unsigned_long_array_pointer);
> +
> +  use (v_float_array_pointer);
> +  use (v_double_array_pointer);
> +
> +  use (v_char_pointer_array);
> +  use (v_signed_char_pointer_array);
> +  use (v_unsigned_char_pointer_array);
> +
> +  use (v_short_pointer_array);
> +  use (v_signed_short_pointer_array);
> +  use (v_unsigned_short_pointer_array);
> +
> +  use (v_int_pointer_array);
> +  use (v_signed_int_pointer_array);
> +  use (v_unsigned_int_pointer_array);
> +
> +  use (v_long_pointer_array);
> +  use (v_signed_long_pointer_array);
> +  use (v_unsigned_long_pointer_array);
> +
> +  use (v_float_pointer_array);
> +  use (v_double_pointer_array);
> +
> +  use (&v_struct1);
> +  use (&v_struct2);
> +  use (&v_struct3);
> +
> +  use (&v_union);
> +  use (&v_union2);
> +  use (&v_union3);
> +
> +  use (&v_boolean);
> +  use (&v_boolean2);
> +  use (&v_misordered);
> +
> +  use (v_char_func);
> +  use (v_signed_char_func);
> +  use (v_unsigned_char_func);
> +
> +  use (v_short_func);
> +  use (v_signed_short_func);
> +  use (v_unsigned_short_func);
> +
> +  use (v_int_func);
> +  use (v_signed_int_func);
> +  use (v_unsigned_int_func);
> +
> +  use (v_long_func);
> +  use (v_signed_long_func);
> +  use (v_unsigned_long_func);
> +
> +  use (v_long_long_func);
> +  use (v_signed_long_long_func);
> +  use (v_unsigned_long_long_func);
> +
> +  use (v_float_func);
> +  use (v_double_func);
>  }

Re: [PATCH] cvexpr.c: Don't let linker delete unused globals

[Kevin Buettner]

On Apr 18, 10:02am, Michael Snyder wrote:

> > On AIX, I was seeing lots of failures in gdb.base/code-expr.exp and
> > gdb.base/cvexpr.exp due to the fact that the linker deletes unused
> > symbols.  The patch below fixes these failures.
> > 
> > Committed as obvious.
> 
> Wow, that's really sad, to have to add all that code
> for such a trivial reason.  I'm sure there are other 
> tests in gdb.base that also make use of symbols that
> don't get called.

Yeah.  I ran across some of these in the past and added some similar
looking code.  E.g, here's a ChangeLog entry for one of them:

2000-03-21  Kevin Buettner <kevinb@redhat.com>

	* gdb.base/pointers.c (usevar): New function.
	(main): Make sure that global variables v_int_pointer2, rptr,
	and y are all referenced someplace in the program by calling
	usevar() on them.  [Some linkers delete symbols which are
	never referenced.  The space remains, but there's no way to
	get a (symbolic) handle on the variable from the debugger.]


> Isn't there some option that you can
> give to the linker to tell it not to remove these?

Apparently there is, but in my opinion, it's easier to maintain
changes to C code than bits of configury involving the linker
which can change over time.  Also, the testsuite will just work
without the need to specify any additional linker options for
other (future) linkers which choose to also garbage collect unused
symbols.

Kevin