68337b8be3
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. |
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README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.