[PATCH 8/9] Use bit stride when taking slice of array

Tom Tromey
2020-09-30T20:06:44Z

Testing with -fgnat-encodings=minimal showed that the Ada code failed
to use the bit stride of an array when taking a slice. This patch
fixes the oversight.

2020-09-30 Tom Tromey <tromey@adacore.com>

* ada-lang.c (ada_value_slice_from_ptr): Use bit size.

gdb/testsuite/ChangeLog
2020-09-30 Tom Tromey <tromey@adacore.com>

* gdb.ada/array_of_variant.exp: New file.
* gdb.ada/array_of_variant/p.adb: New file.
* gdb.ada/array_of_variant/pck.ads: New file.
* gdb.ada/array_of_variant/pck.adb: New file.
---
gdb/ChangeLog | 4 ++
gdb/ada-lang.c | 8 +--
gdb/testsuite/ChangeLog | 7 +++
gdb/testsuite/gdb.ada/array_of_variant.exp | 52 +++++++++++++++++++
gdb/testsuite/gdb.ada/array_of_variant/p.adb | 39 ++++++++++++++
.../gdb.ada/array_of_variant/pck.adb | 23 ++++++++
.../gdb.ada/array_of_variant/pck.ads | 23 ++++++++
7 files changed, 153 insertions(+), 3 deletions(-)
create mode 100644 gdb/testsuite/gdb.ada/array_of_variant.exp
create mode 100644 gdb/testsuite/gdb.ada/array_of_variant/p.adb
create mode 100644 gdb/testsuite/gdb.ada/array_of_variant/pck.adb
create mode 100644 gdb/testsuite/gdb.ada/array_of_variant/pck.ads

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index e81a7877ccb..b06bb68df20 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -2846,9 +2846,11 @@ ada_value_slice_from_ptr (struct value *array_ptr, struct type *type,
base_low_pos = base_low;
}

- base = value_as_address (array_ptr)
- + ((low_pos - base_low_pos)
- * TYPE_LENGTH (TYPE_TARGET_TYPE (type0)));
+ ULONGEST stride = TYPE_FIELD_BITSIZE (slice_type, 0) / 8;
+ if (stride == 0)
+ stride = TYPE_LENGTH (TYPE_TARGET_TYPE (type0));
+
+ base = value_as_address (array_ptr) + (low_pos - base_low_pos) * stride;
return value_at_lazy (slice_type, base);
}

diff --git a/gdb/testsuite/gdb.ada/array_of_variant.exp b/gdb/testsuite/gdb.ada/array_of_variant.exp
new file mode 100644
index 00000000000..f2c343fdab0
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/array_of_variant.exp
@@ -0,0 +1,52 @@
+# Copyright 2020 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/>.
+
+load_lib "ada.exp"
+
+if { [skip_ada_tests] } { return -1 }
+
+standard_ada_testfile p
+
+foreach_with_prefix scenario {all minimal} {
+ set flags [list debug additional_flags=-fgnat-encodings=$scenario]
+
+ if {[gdb_compile_ada "${srcfile}" "${binfile}" executable $flags] != ""} {
+ return -1
+ }
+
+ clean_restart ${testfile}
+
+ set bp_location [gdb_get_line_number "START" ${testdir}/p.adb]
+ runto "p.adb:$bp_location"
+
+ set v1 "(tag => object, values => (2, 2, 2, 2, 2))"
+ set v2 "(tag => unused)"
+
+ gdb_test "print objects" \
+ [string_to_regexp " = ($v1, $v2)"] \
+ "print entire array"
+ gdb_test "print objects(1)" \
+ [string_to_regexp " = $v1"] \
+ "print first array element"
+ gdb_test "print objects(1 .. 1)" \
+ [string_to_regexp " = ($v1)"] \
+ "print first array slice"
+ gdb_test "print objects(2)" \
+ [string_to_regexp " = $v2"] \
+ "print second array element"
+ gdb_test "print objects(2 .. 2)" \
+ [string_to_regexp " = (2 => $v2)"] \
+ "print second array slice"
+}
diff --git a/gdb/testsuite/gdb.ada/array_of_variant/p.adb b/gdb/testsuite/gdb.ada/array_of_variant/p.adb
new file mode 100644
index 00000000000..d9974ef43bf
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/array_of_variant/p.adb
@@ -0,0 +1,39 @@
+-- Copyright 2020 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/>.
+
+with Pck; use Pck;
+
+procedure P is
+
+ type Tag_T is (Unused, Object);
+
+ type Array_T is array (1 .. Five) of Integer;
+
+ type Payload_T (Tag : Tag_T := Unused) is
+ record
+ case Tag is
+ when Object =>
+ Values : Array_T := (others => 1);
+ when Unused =>
+ null;
+ end case;
+ end record;
+
+ Objects : array (1 .. 2) of Payload_T;
+
+begin
+ Objects (1) := (Tag => Object, Values => (others => 2));
+ Do_Nothing (Objects'Address); -- START
+end P;
diff --git a/gdb/testsuite/gdb.ada/array_of_variant/pck.adb b/gdb/testsuite/gdb.ada/array_of_variant/pck.adb
new file mode 100644
index 00000000000..af4fe6d6aa7
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/array_of_variant/pck.adb
@@ -0,0 +1,23 @@
+-- Copyright 2020 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/>.
+
+package body Pck is
+
+ procedure Do_Nothing (A : System.Address) is
+ begin
+ null;
+ end Do_Nothing;
+
+end Pck;
diff --git a/gdb/testsuite/gdb.ada/array_of_variant/pck.ads b/gdb/testsuite/gdb.ada/array_of_variant/pck.ads
new file mode 100644
index 00000000000..f2a676ca205
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/array_of_variant/pck.ads
@@ -0,0 +1,23 @@
+-- Copyright 2020 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/>.
+
+with System;
+
+package Pck is
+ Five : Integer := 5;
+
+ procedure Do_Nothing (A : System.Address);
+
+end Pck;
--
2.26.2