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Fortran function calls with arguments

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Prior to this patch, calling functions on the inferior with arguments and
then using these arguments within a function resulted in an invalid
memory access. This is because Fortran arguments are typically passed as
pointers to values.

It is possible to call Fortran functions, but memory must be allocated in
the inferior, so a pointer can be passed to the function, and the
language must be set to C to enable C-style casting. This is cumbersome
and not a pleasant debug experience.

This patch implements the GNU Fortran argument passing conventions with
caveats. Firstly, it does not handle the VALUE attribute as there is
insufficient DWARF information to determine when this is the case.
Secondly, functions with optional parameters can only be called with all
parameters present. Both these cases are marked as KFAILS in the test.

Since the GNU Fortran argument passing convention has been implemented,
there is no guarantee that this patch will work correctly, in all cases,
with other compilers.

Despite these limitations, this patch improves the ease with which
functions can be called in many cases, without taking away the existing
approach of calling with the language set to C.

Regression tested on x86_64, aarch64 and POWER9 with GCC 7.3.0.
Regression tested with Ada on x86_64.
Regression tested with native-extended-gdbserver target board.

gdb/ChangeLog:

	* eval.c (evaluate_subexp_standard): Call Fortran argument
	wrapping logic.
	* f-lang.c (struct value): A value which can be passed into a
	Fortran function call.
	(fortran_argument_convert): Wrap Fortran arguments in a pointer
	where appropriate.
	(struct type): Value ready for a Fortran function call.
	(fortran_preserve_arg_pointer): Undo check_typedef, the pointer
	is needed.
	* f-lang.h (fortran_argument_convert): Declaration.
	(fortran_preserve_arg_pointer): Declaration.
	* infcall.c (value_arg_coerce): Call Fortran argument logic.

gdb/testsuite/ChangeLog:

	* gdb.fortran/function-calls.exp: New file.
	* gdb.fortran/function-calls.f90: New test.
This commit is contained in:
Richard Bunt
2019-03-06 08:23:00 +00:00
parent 2d0d5fc6f0
commit aa3cfbda2f
8 changed files with 457 additions and 3 deletions
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15
gdb/eval.c
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@@ -1987,7 +1987,20 @@ evaluate_subexp_standard (struct type *expect_type,
argvec[0] = arg1;
tem = 1;
for (; tem <= nargs; tem++)
argvec[tem] = evaluate_subexp_with_coercion (exp, pos, noside);
{
argvec[tem] = evaluate_subexp_with_coercion (exp, pos, noside);
/* Arguments in Fortran are passed by address. Coerce the
arguments here rather than in value_arg_coerce as otherwise
the call to malloc to place the non-lvalue parameters in
target memory is hit by this Fortran specific logic. This
results in malloc being called with a pointer to an integer
followed by an attempt to malloc the arguments to malloc in
target memory. Infinite recursion ensues. */
bool is_artificial =
TYPE_FIELD_ARTIFICIAL (value_type (arg1), tem - 1);
argvec[tem] = fortran_argument_convert (argvec[tem],
is_artificial);
}
argvec[tem] = 0; /* signal end of arglist */
if (noside == EVAL_SKIP)
return eval_skip_value (exp);