Logical short circuiting with argument lists

When evaluating Fortran expressions such as the following:

	print truth_table(1,1) .OR. truth_table(2,1)

where truth_table(1,1) evaluates to true, the debugger would report that
it could not perform substring operations on this type. This patch
addresses this issue.

Investigation revealed that EVAL_SKIP was not being handled correctly
for all types serviced by the OP_F77_UNDETERMINED_ARGLIST case in
evaluate_subexp_standard. While skipping an undetermined argument list
the type is resolved to be an integer (as this is what evaluate_subexp
returns when skipping) and so it was not possible to delegate to the
appropriate case (e.g. array, function call).

The solution implemented here updates OP_VAR_VALUE to return correct
type information when skipping. This way OP_F77_UNDETERMINED_ARGLIST
can delegate the skipping to the appropriate case or routine, which
should know how to skip/evaluate the type in question.

koenig.exp was updated to include a testcase which exercises the
modified skip logic in OP_VAR_VALUE, as it falls through from
OP_ADL_FUNC.

This patch has been tested for regressions with GCC 7.3 on aarch64,
ppc64le and x86_64.

gdb/ChangeLog:

	* eval.c (skip_undetermined_arglist): Skip argument list helper.
	(evaluate_subexp_standard): Return a dummy type when
	honoring EVAL_SKIP in OP_VAR_VALUE and handle skipping in the
	OP_F77_UNDETERMINED_ARGLIST case.
	* expression.h (enum noside): Update comment.

gdb/testsuite/ChangeLog:

	* gdb.cp/koenig.exp: Extend to test logical short circuiting.
	* gdb.fortran/short-circuit-argument-list.exp: New file.
	* gdb.fortran/short-circuit-argument-list.f90: New test.

7 files changed, 243 insertions, 8 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0c75340..8675c15 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2018-09-19  Richard Bunt  <richard.bunt@arm.com>
+	    Chris January  <chris.january@arm.com>
+
+	* eval.c (skip_undetermined_arglist): Skip argument list helper.
+	(evaluate_subexp_standard): Return a dummy type when
+	honoring EVAL_SKIP in OP_VAR_VALUE and handle skipping in the
+	OP_F77_UNDETERMINED_ARGLIST case.
+	* expression.h (enum noside): Update comment.
+
 2018-09-19  George Vasick <george.vasick@oracle.com>
 
 	* solib-svr4.c (svr4_same_1): Also handle amd64 ld.so.1.
diff --git a/gdb/eval.c b/gdb/eval.c
index f9349e6..2144b1d 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -1238,6 +1238,19 @@ evaluate_funcall (type *expect_type, expression *exp, int *pos,
   return eval_call (exp, noside, nargs, argvec, var_func_name, expect_type);
 }
 
+/* Helper for skipping all the arguments in an undetermined argument list.
+   This function was designed for use in the OP_F77_UNDETERMINED_ARGLIST
+   case of evaluate_subexp_standard as multiple, but not all, code paths
+   require a generic skip.  */
+
+static void
+skip_undetermined_arglist (int nargs, struct expression *exp, int *pos,
+			   enum noside noside)
+{
+  for (int i = 0; i < nargs; ++i)
+    evaluate_subexp (NULL_TYPE, exp, pos, noside);
+}
+
 struct value *
 evaluate_subexp_standard (struct type *expect_type,
 			  struct expression *exp, int *pos,
@@ -1286,16 +1299,19 @@ evaluate_subexp_standard (struct type *expect_type,
 
     case OP_ADL_FUNC:
     case OP_VAR_VALUE:
-      (*pos) += 3;
-      if (noside == EVAL_SKIP)
-	return eval_skip_value (exp);
-
       {
+	(*pos) += 3;
 	symbol *var = exp->elts[pc + 2].symbol;
 	if (TYPE_CODE (SYMBOL_TYPE (var)) == TYPE_CODE_ERROR)
 	  error_unknown_type (SYMBOL_PRINT_NAME (var));
-
-	return evaluate_var_value (noside, exp->elts[pc + 1].block, var);
+	if (noside != EVAL_SKIP)
+	    return evaluate_var_value (noside, exp->elts[pc + 1].block, var);
+	else
+	  {
+	    /* Return a dummy value of the correct type when skipping, so
+	       that parent functions know what is to be skipped.  */
+	    return allocate_value (SYMBOL_TYPE (var));
+	  }
       }
 
     case OP_VAR_MSYM_VALUE:
@@ -1933,13 +1949,27 @@ evaluate_subexp_standard (struct type *expect_type,
 	  if (exp->elts[*pos].opcode == OP_RANGE)
 	    return value_f90_subarray (arg1, exp, pos, noside);
 	  else
-	    goto multi_f77_subscript;
+	    {
+	      if (noside == EVAL_SKIP)
+		{
+		  skip_undetermined_arglist (nargs, exp, pos, noside);
+		  /* Return the dummy value with the correct type.  */
+		  return arg1;
+		}
+	      goto multi_f77_subscript;
+	    }
 
 	case TYPE_CODE_STRING:
 	  if (exp->elts[*pos].opcode == OP_RANGE)
 	    return value_f90_subarray (arg1, exp, pos, noside);
 	  else
 	    {
+	      if (noside == EVAL_SKIP)
+		{
+		  skip_undetermined_arglist (nargs, exp, pos, noside);
+		  /* Return the dummy value with the correct type.  */
+		  return arg1;
+		}
 	      arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
 	      return value_subscript (arg1, value_as_long (arg2));
 	    }
diff --git a/gdb/expression.h b/gdb/expression.h
index 9f26bb8..bc7625f 100644
--- a/gdb/expression.h
+++ b/gdb/expression.h
@@ -118,7 +118,9 @@ extern int parse_completion;
 enum noside
   {
     EVAL_NORMAL,
-    EVAL_SKIP,			/* Only effect is to increment pos.  */
+    EVAL_SKIP,			/* Only effect is to increment pos.
+				   Return type information where
+				   possible.  */
     EVAL_AVOID_SIDE_EFFECTS	/* Don't modify any variables or
 				   call any functions.  The value
 				   returned will have the correct
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 701d979..37f252e 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-19  Richard Bunt  <richard.bunt@arm.com>
+	    Chris January  <chris.january@arm.com>
+
+	* gdb.cp/koenig.exp: Extend to test logical short circuiting.
+	* gdb.fortran/short-circuit-argument-list.exp: New file.
+	* gdb.fortran/short-circuit-argument-list.f90: New test.
+
 2018-09-18  Sergio Durigan Junior  <sergiodj@redhat.com>
 
 	* gdb.arch/amd64-invalid-stack-top.exp: Expect optional
diff --git a/gdb/testsuite/gdb.cp/koenig.exp b/gdb/testsuite/gdb.cp/koenig.exp
index b7dff90..0725c1b 100644
--- a/gdb/testsuite/gdb.cp/koenig.exp
+++ b/gdb/testsuite/gdb.cp/koenig.exp
@@ -33,6 +33,9 @@ gdb_test "p first(c)" "= 11"
 # the qualifying parameter
 gdb_test "p second(0,0,c,0,0)" "= 33"
 
+# Test evaluating function under EVAL_SKIP
+gdb_test "p true || second(0,0,c,0,0)" "= true"
+
 # Test the name "entry" being used for `variablename@entry' entry values.
 gdb_test "p entry (c)" " = 44"
 
diff --git a/gdb/testsuite/gdb.fortran/short-circuit-argument-list.exp b/gdb/testsuite/gdb.fortran/short-circuit-argument-list.exp
new file mode 100644
index 0000000..1b948bb
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/short-circuit-argument-list.exp
@@ -0,0 +1,106 @@
+# Copyright 2018 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/> .
+
+# Test evaluating logical expressions that contain array references, function
+# calls and substring operations that are to be skipped due to short
+# circuiting.
+
+if {[skip_fortran_tests]} { return -1 }
+
+standard_testfile ".f90"
+
+if {[prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} {debug f90}]} {
+    return -1
+}
+
+if {![runto [gdb_get_line_number "post_truth_table_init"]]} then {
+    perror "couldn't run to breakpoint post_truth_table_init"
+    continue
+}
+
+# Vary conditional and input over the standard truth table.
+# Test that the debugger can evaluate expressions of the form
+# a(x,y) .OR./.AND. a(a,b) correctly.
+foreach_with_prefix truth_table_index {1 2 3 4} {
+    gdb_test "p truth_table($truth_table_index, 1) .OR. truth_table($truth_table_index, 2)" \
+	     "[expr $truth_table_index > 1 ? \".TRUE.\" : \".FALSE.\"]"
+}
+
+foreach_with_prefix truth_table_index {1 2 3 4} {
+    gdb_test "p truth_table($truth_table_index, 1) .AND. truth_table($truth_table_index, 2)" \
+	     "[expr $truth_table_index > 3 ? \".TRUE.\" : \".FALSE.\"]"
+}
+
+# Vary number of function arguments to skip.
+set argument_list ""
+foreach_with_prefix arg {"No" "One" "Two"} {
+    set trimmed_args [string trimright $argument_list ,]
+    set arg_lower [string tolower $arg]
+    gdb_test "p function_no_arg_false() .OR. function_${arg_lower}_arg($trimmed_args)" \
+	     " $arg, return true.\r\n\\\$$decimal = .TRUE."
+    # Check the skipped function has not printed anything by asserting the
+    # absence of the full stop from its message.
+    gdb_test "p .TRUE. .OR. function_${arg_lower}_arg($trimmed_args)" \
+	     "\[^.\]\r\n\\\$$decimal = .TRUE."
+    append argument_list " .TRUE.,"
+}
+
+# Check nested calls
+gdb_test "p function_one_arg(.FALSE. .OR. function_no_arg())" \
+	 " No, return true.\r\n One, return true.\r\n\\\$$decimal = .TRUE."
+
+gdb_test "p function_one_arg(.TRUE. .OR. function_no_arg())" \
+	 "\[^.\]\r\n One, return true.\r\n\\\$$decimal = .TRUE."
+
+# Vary number of components in the expression to skip.
+set expression "p .TRUE."
+foreach_with_prefix expression_components {1 2 3 4} {
+    set expression "$expression .OR. function_one_arg(.TRUE.)"
+    gdb_test "$expression" \
+	     "\\\$$decimal = .TRUE."
+}
+
+# Check parsing skipped substring operations.
+gdb_test "p .TRUE. .OR. binary_string(1)" "\\\$$decimal = .TRUE."
+
+# Check parsing skipped substring operations with ranges. These should all
+# return true as the result is > 0.
+# The second binary_string access is important as an incorrect pos update
+# will not be picked up by a single access.
+foreach_with_prefix range1 {"1:2" ":" ":2" "1:"} {
+    foreach_with_prefix range2 {"1:2" ":" ":2" "1:"} {
+	gdb_test "p .TRUE. .OR. binary_string($range1) .OR. binary_string($range2)" \
+		 "\\\$$decimal = .TRUE."
+    }
+}
+
+# Skip multi-dimensional arrays with ranges.
+foreach_with_prefix range1 {"1:2" ":" ":2" "1:"} {
+    foreach_with_prefix range2 {"1:2" ":" ":2" "1:"} {
+	gdb_test "p .TRUE. .OR. binary_string($range1) .OR. truth_table($range2, 1)" \
+		 "\\\$$decimal = .TRUE."
+    }
+}
+
+# Check evaluation of substring operations in logical expressions.
+gdb_test "p .FALSE. .OR. binary_string(1)" "\\\$$decimal = .FALSE."
+
+# Function call and substring skip.
+gdb_test "p .TRUE. .OR. function_one_arg(binary_string(1))" \
+	 "\\\$$decimal = .TRUE."
+
+# Function call and array skip.
+gdb_test "p .TRUE. .OR. function_array(binary_string)" \
+	 "\\\$$decimal = .TRUE."
diff --git a/gdb/testsuite/gdb.fortran/short-circuit-argument-list.f90 b/gdb/testsuite/gdb.fortran/short-circuit-argument-list.f90
new file mode 100644
index 0000000..5d8b9c7
--- /dev/null
+++ b/gdb/testsuite/gdb.fortran/short-circuit-argument-list.f90
@@ -0,0 +1,78 @@
+! Copyright 2018 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/> .
+
+! Source code for short-circuit-argument-list.exp.
+
+logical function function_no_arg()
+    print *, "No, return true."
+    function_no_arg = .TRUE.
+end function function_no_arg
+
+logical function function_no_arg_false()
+    function_no_arg_false = .FALSE.
+end function function_no_arg_false
+
+logical function function_one_arg(x)
+    logical, intent(in) :: x
+    print *, "One, return true."
+    function_one_arg = .TRUE.
+end function function_one_arg
+
+logical function function_two_arg(x, y)
+    logical, intent(in) :: x, y
+    print *, "Two, return true."
+    function_two_arg = .TRUE.
+end function function_two_arg
+
+logical function function_array(logical_array)
+    logical, dimension(4,2), target, intent(in) :: logical_array
+    logical, dimension(:,:), pointer :: p
+    p => logical_array
+    print *, "Array, return true.", p(1,1), logical_array(1,1)
+    function_array = .TRUE.
+end function function_array
+
+program generate_truth_table
+    implicit none
+    interface
+	logical function function_no_arg()
+	end function function_no_arg
+	logical function function_no_arg_false()
+	end function
+	logical function function_one_arg(x)
+	    logical, intent(in) :: x
+	end function
+	logical function function_two_arg(x, y)
+	    logical, intent(in) :: x, y
+	end function
+	logical function function_array(logical_array)
+	    logical, dimension(4,2), target, intent(in) :: logical_array
+	end function function_array
+    end interface
+    logical, dimension (4,2) :: truth_table
+    logical :: a, b, c, d, e
+    character(2) :: binary_string
+    binary_string = char(0) // char(1)
+    truth_table = .FALSE.
+    truth_table(3:4,1) = .TRUE.
+    truth_table(2::2,2) = .TRUE.
+    a = function_no_arg() ! post_truth_table_init
+    b = function_no_arg_false()
+    c = function_one_arg(b)
+    d = function_two_arg(a, b)
+    e = function_array(truth_table)
+    print *, truth_table(:, 1), a, b, e
+    print *, truth_table(:, 2), c, d
+end program generate_truth_table