[binutils-gdb] gdb: Allow address space qualifier parsing in C++.

[binutils-gdb] gdb: Allow address space qualifier parsing in C++.

[Felix Willgerodt]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=525174e886044ce3538b13545939421032f77a1b

commit 525174e886044ce3538b13545939421032f77a1b
Author: Felix Willgerodt <felix.willgerodt@intel.com>
Date:   Tue Apr 20 08:43:08 2021 +0200

    gdb: Allow address space qualifier parsing in C++.
    
    The goal of this patch is to allow target dependent address space qualifiers
    in the C++ expression parser.  This can be useful for memory examination on
    targets that actually use different address spaces in hardware without
    having to deep-dive into implementation details of the whole solution.
    
    GDB uses the @ symbol to parse address space qualifiers.  The only current
    user that I am aware of is the __flash support for avr, which was added in
    "Add support for the __flash qualifier on AVR"
    (487d975399dfcb2bb2f0998a7d12bd62acdd9fa1)
    and only works for C.
    
    One use-case of the AVR patch is:
    
    ~~~
    const __flash char data_in_flash = 0xab;
    
    int
    main (void)
    {
      const __flash char *pointer_to_flash = &data_in_flash;
    }
    ~~~
    
    ~~~
    (gdb) print pointer_to_flash
    $1 = 0x1e8 <data_in_flash> "\253"
    (gdb) print/x *pointer_to_flash
    $2 = 0xab
    (gdb) x/x pointer_to_flash
    0x1e8 <data_in_flash>: 0xXXXXXXab
    (gdb)
    (gdb) p/x *(char* @flash) pointer_to_flash
    $3 = 0xab
    ~~~
    
    I want to enable a similar usage of e.g. @local in C++.
    
    Before this patch (using "set debug parser on"):
    
    ~~~
    (gdb) p *(int* @local) 0x1234
    (...)
    Reading a token: Next token is token '@' ()
    Shifting token '@' ()
    Entering state 46
    Reading a token: Next token is token UNKNOWN_CPP_NAME (ssym<name=local, sym=(null), field_of_this=0>)
    A syntax error in expression, near `local) &x'.
    ~~~
    
    After:
    ~~~
    (gdb) p *(int* @local) 0x1234
    (...)
    Reading a token: Next token is token '@' ()
    Shifting token '@' ()
    Entering state 46
    Reading a token: Next token is token UNKNOWN_CPP_NAME (ssym<name=local, sym=(null), field_of_this=0>)
    Shifting token UNKNOWN_CPP_NAME (ssym<name=local, sym=(null), field_of_this=0>)
    Entering state 121
    Reducing stack by rule 278 (line 1773):
       $1 = token UNKNOWN_CPP_NAME (ssym<name=local, sym=(null), field_of_this=0>)
    -> $$ = nterm name ()
    Stack now 0 49 52 76 222 337 46
    Entering state 167
    Reducing stack by rule 131 (line 1225):
       $1 = token '@' ()
       $2 = nterm name ()
    Unknown address space specifier: "local"
    ~~~
    
    The "Unknown address space qualifier" is the right behaviour, as I ran this
    on a target that doesn't have multiple address spaces and therefore obviously
    no support for such qualifiers.
    
    gdb/ChangeLog:
    2021-04-20  Felix Willgerodt  <felix.willgerodt@intel.com>
    
            * c-exp.y (single_qualifier): Handle UNKNOWN_CPP_NAME.
    
    gdb/testsuite/ChangeLog:
    2021-04-20  Felix Willgerodt  <felix.willgerodt@intel.com>
    
            * gdb.base/address_space_qualifier.exp: New file.

Diff:
---
 gdb/ChangeLog                                      |  4 +++
 gdb/c-exp.y                                        |  5 ++++
 gdb/testsuite/ChangeLog                            |  4 +++
 gdb/testsuite/gdb.base/address_space_qualifier.exp | 35 ++++++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a7f079e70e3..8692c0f8c43 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2021-04-20  Felix Willgerodt  <felix.willgerodt@intel.com>
+
+	* c-exp.y (single_qualifier): Handle UNKNOWN_CPP_NAME.
+
 2021-04-19  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* producer.c: Replace 'regex' include with 'gdb_regex.h'.
diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index 865b1554de1..3e416f4e2c7 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -1267,6 +1267,11 @@ single_qualifier:
 		  cpstate->type_stack.insert (pstate,
 					      copy_name ($2.stoken).c_str ());
 		}
+	|	'@' UNKNOWN_CPP_NAME
+		{
+		  cpstate->type_stack.insert (pstate,
+					      copy_name ($2.stoken).c_str ());
+		}
 	;
 
 qualifier_seq_noopt:
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 2bc845c0275..68e46652581 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2021-04-20  Felix Willgerodt  <felix.willgerodt@intel.com>
+
+	* gdb.base/address_space_qualifier.exp: New file.
+
 2021-04-19  Tom Tromey  <tromey@adacore.com>
 
 	PR gdb/27742:
diff --git a/gdb/testsuite/gdb.base/address_space_qualifier.exp b/gdb/testsuite/gdb.base/address_space_qualifier.exp
new file mode 100644
index 00000000000..b8209dc565b
--- /dev/null
+++ b/gdb/testsuite/gdb.base/address_space_qualifier.exp
@@ -0,0 +1,35 @@
+# 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/>.  */
+
+# Regression test for expression evaluation of address space qualifiers
+# in C and C++.
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+
+gdb_test_no_output "set language c"
+
+with_test_prefix "C" {
+	gdb_test "p *(@somerandomqualifiername int *) 0x12345678" \
+		"Unknown address space specifier: \"somerandomqualifiername\""
+}
+
+gdb_test_no_output "set language c++"
+
+with_test_prefix "C++" {
+	gdb_test "p *(@somerandomqualifiername int *) 0x12345678" \
+		"Unknown address space specifier: \"somerandomqualifiername\""
+}