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When attempting to call a Fortran function for which there is no debug information we currently trigger undefined behaviour in GDB by accessing non-existent type fields. The reason is that in order to prepare the arguments, for a call to a Fortran function, we need to know the type of each argument. If the function being called has no debug information then obviously GDB doesn't know about the argument types and we should either give the user an error or pick a suitable default. What we currently do is just assume the field exist and access undefined memory, which is clearly wrong. The reason GDB needs to know the argument type is to tell if the argument is artificial or not, artificial arguments will be passed by value while non-artificial arguments will be passed by reference. An ideal solution for this problem would be to allow the user to cast the function to the correct type, we already do this to some degree with the return value, for example: (gdb) print some_func_ () 'some_func_' has unknown return type; cast the call to its declared return type (gdb) print (integer) some_func_ () $1 = 1 But if we could extend this to allow casting to the full function type, GDB could figure out from the signature what are real parameters, and what are artificial parameters. Maybe something like this: (gdb) print ((integer () (integer, double)) some_other_func_ (1, 2.3) Alas, right now the Fortran expression parser doesn't seem to support parsing function signatures, and we certainly don't have support for figuring out real vs artificial arguments from a signature. Still, I think we can prevent GDB from accessing undefined memory and provide a reasonable default behaviour. In this commit I: - Only ask if the argument is artificial if the type of the argument is actually known. - Unknown arguments are assumed to be artificial and passed by value (non-artificial arguments are pass by reference). - If an artificial argument is prefixed with '&' by the user then we treat the argument as pass-by-reference. With these three changes we avoid undefined behaviour in GDB, and allow the user, in most cases, to get a reasonably natural default behaviour. gdb/ChangeLog: PR fortran/26155 * f-lang.c (fortran_argument_convert): Delete declaration. (fortran_prepare_argument): New function. (evaluate_subexp_f): Move logic to new function fortran_prepare_argument. gdb/testsuite/ChangeLog: PR fortran/26155 * gdb.fortran/call-no-debug-func.f90: New file. * gdb.fortran/call-no-debug-prog.f90: New file. * gdb.fortran/call-no-debug.exp: New file.
36 lines
1.0 KiB
Fortran
36 lines
1.0 KiB
Fortran
! Copyright 2020-2021 Free Software Foundation, Inc.
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!
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! This program is free software; you can redistribute it and/or modify
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! it under the terms of the GNU General Public License as published by
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! the Free Software Foundation; either version 3 of the License, or
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! (at your option) any later version.
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!
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! This program is distributed in the hope that it will be useful,
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! but WITHOUT ANY WARRANTY; without even the implied warranty of
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! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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! GNU General Public License for more details.
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!
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! You should have received a copy of the GNU General Public License
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! along with this program. If not, see <http://www.gnu.org/licenses/>.
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program main
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implicit none
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interface
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integer function some_func (arg)
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integer :: arg
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end function some_func
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integer function string_func (str)
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character(len=*) :: str
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end function string_func
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end interface
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integer :: val
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val = some_func (1)
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print *, val
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val = string_func ('hello')
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print *, val
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end program main
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