[PATCHv2,1/3] gdb: fix regression in evaluate_funcall for non C++ like cases

Message ID 55ab7334096e7db71329cea80a544dfdb4d83db8.1624451048.git.andrew.burgess@embecosm.com
State Superseded
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  • [PATCHv2,1/3] gdb: fix regression in evaluate_funcall for non C++ like cases
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Commit Message

Andrew Burgess June 23, 2021, 12:26 p.m.
This regression, as it is exposed by the test added in this commit,
first became noticable with this commit:

  commit d182f2797922a305fbd1ef6a483cc39a56b43e02
  Date:   Mon Mar 8 07:27:57 2021 -0700

      Convert c-exp.y to use operations

But, this commit only added converted the C expression parser to make
use of code that was added in this commit:

  commit a00b7254fb614af557de7ae7cc0eb39a0ce0e408
  Date:   Mon Mar 8 07:27:57 2021 -0700

      Implement function call operations

And it was this second commit that actually introduced the bugs (there
are two).

In structop_base_operation::evaluate_funcall we build up an argument
list in the vector vals.  Later in this function the argument list
might be passed to value_struct_elt.

Prior to commit a00b7254fb614 the vals vector (or argvec as it used to
be called) stored the value for the function callee in the argvec at
index 0.  This 'callee' value is what ends up being passed to
evaluate_subexp_do_call, and represents the function to be called, the
value contents are the address of the function, and the value type is
the function signature.  The remaining items held in the argvec were
the values to pass to the function.  For a non-static member function
the `this' pointer would be at index 1 in the array.

After commit a00b7254fb614 this callee value is now held in a separate
variable, not the vals array.  So, for non-static member functions,
the `this' pointer is now at index 0, with any other arguments after
that.

What this means is that previous, when we called value_struct_elt we
would pass the address of argvec[1] as this was the first argument.
But now we should be passing the address of vals[0].  Unfortunately,
we are still passing vals[1], effectively skipping the first
argument.

The second issue is that, prior to commit a00b7254fb614, the argvec
array was NULL terminated.  This is required as value_struct_elt
calls search_struct_method, which calls typecmp, and typecmp requires
that the array have a NULL at the end.

After commit a00b7254fb614 this NULL has been lost, and we are
therefore violating the API requirements of typecmp.

This commit fixes both of these regressions.  I also extended the
header comments on search_struct_method and value_struct_elt to make
it clearer that the array required a NULL marker at the end.

gdb/ChangeLog:

	PR gdb/27994
	* eval.c (structop_base_operation::evaluate_funcall): Add a
	nullptr to the end of the args array, which should not be included
	in the argument array_view.  Pass all the arguments through to
	value_struct_elt.
	* valops.c (search_struct_method): Update header comment.
	(value_struct_elt): Likewise.

gdb/testsuite/ChangeLog:

	PR gdb/27994
	* gdb.cp/method-call-in-c.cc: New file.
	* gdb.cp/method-call-in-c.exp: New file.
---
 gdb/ChangeLog                             | 10 ++++++
 gdb/eval.c                                | 15 ++++++--
 gdb/testsuite/ChangeLog                   |  6 ++++
 gdb/testsuite/gdb.cp/method-call-in-c.cc  | 44 +++++++++++++++++++++++
 gdb/testsuite/gdb.cp/method-call-in-c.exp | 44 +++++++++++++++++++++++
 gdb/valops.c                              |  7 +++-
 6 files changed, 122 insertions(+), 4 deletions(-)
 create mode 100644 gdb/testsuite/gdb.cp/method-call-in-c.cc
 create mode 100644 gdb/testsuite/gdb.cp/method-call-in-c.exp

-- 
2.25.4

Comments

Eli Zaretskii via Gdb-patches June 23, 2021, 3:59 p.m. | #1
> diff --git a/gdb/testsuite/gdb.cp/method-call-in-c.exp b/gdb/testsuite/gdb.cp/method-call-in-c.exp

> new file mode 100644

> index 00000000000..eb48979e465

> --- /dev/null

> +++ b/gdb/testsuite/gdb.cp/method-call-in-c.exp

> @@ -0,0 +1,44 @@

> +# Copyright 2021 Free Software Foundation, Inc.

> +

> +# This program is free software; you can redistribute it and/or modify

> +# it under the terms of the GNU General Public License as published by

> +# the Free Software Foundation; either version 3 of the License, or

> +# (at your option) any later version.

> +#

> +# This program is distributed in the hope that it will be useful,

> +# but WITHOUT ANY WARRANTY; without even the implied warranty of

> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

> +# GNU General Public License for more details.

> +#

> +# You should have received a copy of the GNU General Public License

> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.

> +

> +# Ensure that calling a member function works correctly even when the

> +# language is forced to 'C' (this should be fine, so long at no

> +# overload resolution is required), or when overload-resolution is

> +# off.

> +

> +standard_testfile .cc

> +

> +if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {

> +    return -1

> +}

> +

> +if ![runto_main] then {

> +    return 0

> +}

> +

> +gdb_breakpoint [gdb_get_line_number "Break here"]

> +gdb_continue_to_breakpoint "Break here"

> +

> +set result 123

> +foreach_with_prefix lang { c++ c } {

> +    foreach_with_prefix overload_resolution { on off } {

> +	gdb_test_no_output "set overload-resolution ${overload_resolution}"

> +	gdb_test "set language ${lang}" ".*"


You can simply omit the ".*".

> +

> +	gdb_test "print foo.func (b, f)" " = ${result}" \

> +	    "call foo.func with language auto;c++, overload-resolution on"


The test name looks wrong.

Otherwise, LGTM.

Simon

Patch

diff --git a/gdb/eval.c b/gdb/eval.c
index 659493c8237..ab070a3d9f6 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -872,7 +872,9 @@  structop_base_operation::evaluate_funcall
      (struct type *expect_type, struct expression *exp, enum noside noside,
       const std::vector<operation_up> &args)
 {
-  std::vector<value *> vals (args.size () + 1);
+  /* Allocate space for the function call arguments.  Include space for a
+     `this' pointer at the start, and a trailing nullptr.  */
+  std::vector<value *> vals (args.size () + 2);
   /* First, evaluate the structure into vals[0].  */
   enum exp_opcode op = opcode ();
   if (op == STRUCTOP_STRUCT)
@@ -918,9 +920,16 @@  structop_base_operation::evaluate_funcall
 	}
     }
 
+  /* Evaluate the arguments, and add the trailing nullptr.  The '+ 1' here
+     is to allow for the `this' pointer we placed into vals[0].  */
   for (int i = 0; i < args.size (); ++i)
     vals[i + 1] = args[i]->evaluate_with_coercion (exp, noside);
-  gdb::array_view<value *> arg_view = vals;
+  vals[args.size () + 1] = nullptr;
+
+  /* The array view includes the `this' pointer, but not the trailing
+     nullptr.  */
+  gdb::array_view<value *> arg_view
+    = gdb::make_array_view (&vals[0], args.size () + 1);
 
   int static_memfuncp;
   value *callee;
@@ -941,7 +950,7 @@  structop_base_operation::evaluate_funcall
     {
       struct value *temp = vals[0];
 
-      callee = value_struct_elt (&temp, &vals[1], tstr,
+      callee = value_struct_elt (&temp, &vals[0], tstr,
 				 &static_memfuncp,
 				 op == STRUCTOP_STRUCT
 				 ? "structure" : "structure pointer");
diff --git a/gdb/testsuite/gdb.cp/method-call-in-c.cc b/gdb/testsuite/gdb.cp/method-call-in-c.cc
new file mode 100644
index 00000000000..09e4285ed5d
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/method-call-in-c.cc
@@ -0,0 +1,44 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+struct baz_type
+{
+  int a = 0;
+  int b = 1;
+  int c = 2;
+};
+
+struct foo_type
+{
+  int func (baz_type b, float f)
+  {
+    return var++;
+  }
+
+  int var = 123;
+};
+
+int
+main (void)
+{
+  baz_type b = {};
+  float f = 1.0;
+
+  foo_type foo;
+
+  return foo.func (b, f);	/* Break here.  */
+}
diff --git a/gdb/testsuite/gdb.cp/method-call-in-c.exp b/gdb/testsuite/gdb.cp/method-call-in-c.exp
new file mode 100644
index 00000000000..eb48979e465
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/method-call-in-c.exp
@@ -0,0 +1,44 @@ 
+# Copyright 2021 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Ensure that calling a member function works correctly even when the
+# language is forced to 'C' (this should be fine, so long at no
+# overload resolution is required), or when overload-resolution is
+# off.
+
+standard_testfile .cc
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+    return -1
+}
+
+if ![runto_main] then {
+    return 0
+}
+
+gdb_breakpoint [gdb_get_line_number "Break here"]
+gdb_continue_to_breakpoint "Break here"
+
+set result 123
+foreach_with_prefix lang { c++ c } {
+    foreach_with_prefix overload_resolution { on off } {
+	gdb_test_no_output "set overload-resolution ${overload_resolution}"
+	gdb_test "set language ${lang}" ".*"
+
+	gdb_test "print foo.func (b, f)" " = ${result}" \
+	    "call foo.func with language auto;c++, overload-resolution on"
+	incr result
+    }
+}
diff --git a/gdb/valops.c b/gdb/valops.c
index 8694c124b52..2b579304204 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -2181,6 +2181,10 @@  search_struct_field (const char *name, struct value *arg1,
    ARG1 by OFFSET bytes, and search in it assuming it has (class) type
    TYPE.
 
+   The ARGS array is a list of argument values used to help finding NAME,
+   though ARGS can be nullptr.  If ARGS is not nullptr then the list itself
+   must have a NULL at the end.
+
    If found, return value, else if name matched and args not return
    (value) -1, else return NULL.  */
 
@@ -2309,7 +2313,8 @@  search_struct_method (const char *name, struct value **arg1p,
    ERR is used in the error message if *ARGP's type is wrong.
 
    C++: ARGS is a list of argument types to aid in the selection of
-   an appropriate method.  Also, handle derived types.
+   an appropriate method.  Also, handle derived types.  The array ARGS must
+   have a NULL at the end.
 
    STATIC_MEMFUNCP, if non-NULL, points to a caller-supplied location
    where the truthvalue of whether the function that was resolved was