2016-01-01 04:33:14 +00:00
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# Copyright 2015-2016 Free Software Foundation, Inc.
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[Ada] Enhance type printing for arrays with variable-sized elements
This change is relevant only for standard DWARF (as opposed to the GNAT
encodings extensions): at the time of writing it only makes a difference
with GCC patches that are to be integrated: see the patch series
submission at
<https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01353.html>.
Given the following Ada declarations:
subtype Small_Int is Natural range 0 .. 100;
type R_Type (L : Small_Int := 0) is record
S : String (1 .. L);
end record;
type A_Type is array (Natural range <>) of R_Type;
A : A_Type := (1 => (L => 0, S => ""),
2 => (L => 2, S => "ab"));
Before this change, we would get the following GDB session:
(gdb) ptype a
type = array (1 .. 2) of foo.r_type <packed: 838-bit elements>
This is wrong: "a" is not a packed array. This output comes from the
fact that, because R_Type has a dynamic size (with a maximum), the
compiler has to describe in the debugging information the size allocated
for each array element (i.e. the stride, in DWARF parlance: see
DW_AT_byte_stride). Ada type printing currently assumes that arrays
with a stride are packed, hence the above output.
In practice, GNAT never performs bit-packing for arrays that contain
variable-sized elements. Leveraging this fact, this patch enhances type
printing so that ptype does not pretend that arrays are packed when they
have a stride and they contain dynamic elements. After this change, we
get the following expected output:
(gdb) ptype a
type = array (1 .. 2) of foo.r_type
gdb/ChangeLog:
* ada-typeprint.c (print_array_type): Do not describe arrays as
packed when they embed dynamic elements.
gdb/testsuite/ChangeLog:
* gdb.ada/array_of_variable_length.exp: New testcase.
* gdb.ada/array_of_variable_length/foo.adb: New file.
* gdb.ada/array_of_variable_length/pck.adb: New file.
* gdb.ada/array_of_variable_length/pck.ads: New file.
Tested on x86_64-linux, no regression.
2015-09-15 09:56:03 +00:00
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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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load_lib "ada.exp"
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standard_ada_testfile foo
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if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug]] != "" } {
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return -1
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}
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clean_restart ${testfile}
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set bp_location [gdb_get_line_number "BREAK" ${testdir}/foo.adb]
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runto "foo.adb:$bp_location"
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# Pck.A is an array that embeds elements with variable size so compilers will
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# emit DWARF attributes such as DW_AT_byte_stride to tell GDB how to fetch
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# individual elements. Array stride is also a way to describe packed arrays:
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# make sure we do not consider Pck.A as a packed array.
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gdb_test "ptype pck.a" "array \\(1 \\.\\. 2\\) of pck\\.r_type"
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# Make sure this also works with a type from a fully evaluated value. During
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# evaluation, dynamic types can be "resolved" so GDB internals could "forget"
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# that elements have variable size. Fortunately, type resolution of array
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# elements happens only when processing individual elements (i.e. the resolved
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# array type is still associated to the dynamic element type), so the following
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# is supposed to work.
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gdb_test "print pck.a" \
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"= \\(\\(l => 0, s => \"\"\\), \\(l => 2, s => \"ab\"\\)\\)"
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gdb_test "ptype $"\
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"array \\(1 \\.\\. 2\\) of pck\\.r_type"
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