Re: [RFA/Ada] Allow 'thread' to be used as a variable name in expressions.

[Paul Hilfinger <Hilfinger@adacore.com>]

Joel,

OK.  I have made the requested format changes and added a test.

-- 
Paul N. Hilfinger
(Hilfinger@adacore.com)

--------------------------------------------------


GDB treats the identifiers 'if', 'thread', and 'task' unconditionally
as expression delimiters in Ada mode, which is correct for 'if' and 'task',
but wrong for 'thread' in cases such as

      print thread

Borrowing from c-exp.y, we observe that 'thread' must be followed by
numerals, whereas identifiers never are and treat them as delimiters
only in that case.

In the process, the current also refactors and incidentally fixes the
code for rewinding the input to before the delimiting tokens.  For
example, the code

      watch expr if i > 2

fails because the input is only rewound to just before the 'i',
leaving the 'if' as part of the expression (and thus making the
rest look like trailing junk rather than a conditional clause).

gdb/ChangeLog:

    * ada-lex.l (rules): Only recognize 'thread' as a
    delimiter when followed by numerals, as for c-exp.y.
    Use new rewind_to_char function to rewind the input for
    expression-delimiting tokens.
    (rewind_to_char): New function.

gdb/testsuite/ChangeLog:

    * gdb.ada/expr_delims.exp: New file.
    * gdb.ada/expr_delims/foo.adb: New file.
---
 gdb/ada-lex.l                             |   39 +++++++++++++-----
 gdb/testsuite/gdb.ada/expr_delims.exp     |   64 +++++++++++++++++++++++++++++
 gdb/testsuite/gdb.ada/expr_delims/foo.adb |   26 ++++++++++++
 3 files changed, 118 insertions(+), 11 deletions(-)
 create mode 100644 gdb/testsuite/gdb.ada/expr_delims.exp
 create mode 100644 gdb/testsuite/gdb.ada/expr_delims/foo.adb

diff --git a/gdb/ada-lex.l b/gdb/ada-lex.l
index 2bad4a1..e4d72f2 100644
--- a/gdb/ada-lex.l
+++ b/gdb/ada-lex.l
@@ -53,6 +53,7 @@ static int processReal (const char *);
 static struct stoken processId (const char *, int);
 static int processAttribute (const char *);
 static int find_dot_all (const char *);
+static void rewind_to_char (int);
 
 #undef YY_DECL
 #define YY_DECL static int yylex ( void )
@@ -157,18 +158,19 @@ static int find_dot_all (const char *);
 
 
 if		{
-		  while (*lexptr != 'i' && *lexptr != 'I')
-		    lexptr -= 1;
-		  yyrestart(NULL);
+                  rewind_to_char ('i');
 		  return 0;
 		}
 
-(task|thread)	{
+task            {
+                  rewind_to_char ('t');
+		  return 0;
+		}
+
+thread{WHITE}+{DIG} {
                   /* This keyword signals the end of the expression and
                      will be processed separately.  */
-		  while (*lexptr != 't' && *lexptr != 'T')
-		    lexptr--;
-		  yyrestart(NULL);
+                  rewind_to_char ('t');
 		  return 0;
 		}
 
@@ -218,8 +220,7 @@ false		{ return FALSEKEYWORD; }
 
 ","		{ if (paren_depth == 0 && comma_terminates)
 		    {
-		      lexptr -= 1;
-		      yyrestart(NULL);
+		      rewind_to_char (',');
 		      return 0;
 		    }
 		  else
@@ -229,8 +230,7 @@ false		{ return FALSEKEYWORD; }
 "("		{ paren_depth += 1; return '('; }
 ")"		{ if (paren_depth == 0)
 		    {
-		      lexptr -= 1;
-		      yyrestart(NULL);
+		      rewind_to_char (')');
 		      return 0;
 		    }
 		  else
@@ -616,6 +616,23 @@ processAttribute (const char *str)
   return attributes[k].code;
 }
 
+/* Back up lexptr by yyleng and then to the rightmost occurrence of
+   character CH, case-folded (there must be one).  WARNING: since
+   lexptr points to the next input character that Flex has not yet
+   transferred to its internal buffer, the use of this function
+   depends on the assumption that Flex calls YY_INPUT only when it is
+   logically necessary to do so (thus, there is no reading ahead
+   farther than needed to identify the next token.)  */
+
+static void
+rewind_to_char (int ch)
+{
+  lexptr -= yyleng;
+  while (toupper (*lexptr) != toupper (ch))
+    lexptr -= 1;
+  yyrestart (NULL);
+}
+
 int
 yywrap(void)
 {
diff --git a/gdb/testsuite/gdb.ada/expr_delims.exp b/gdb/testsuite/gdb.ada/expr_delims.exp
new file mode 100644
index 0000000..9e3aeb9
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/expr_delims.exp
@@ -0,0 +1,64 @@
+# Copyright 2012-2013 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"
+
+standard_ada_testfile foo
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug ]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set ws "\[ \t\r\n\]+"
+
+# Start the program in order to have some tasks running...
+set bp_location [gdb_get_line_number "STOP_HERE" ${testdir}/foo.adb]
+gdb_test "break foo.adb:$bp_location" \
+    "Breakpoint $decimal.*" \
+
+gdb_run_cmd
+gdb_test "" "Breakpoint $decimal, foo \\(\\).*"
+gdb_test "continue" \
+         "Continuing\\..*Breakpoint $decimal, foo \\(\\).*"
+
+# Make sure that "thread" may be used as a variable without being mistaken
+# for an expression delimiter.
+gdb_test "print thread" \
+         "= 1" \
+         "Print variable 'thread'"
+
+gdb_test_no_output "delete 1"
+
+gdb_test "watch thread" \
+         ".*atchpoint \[0-9\]+: thread" \
+         "Set plain watchpoint on variable 'thread'"
+
+# Make sure that 'if' when followed by an expression beginning
+# with 'i' works.
+gdb_test "watch thread if i = 2" \
+         ".*atchpoint \[0-9\]+: thread" \
+         "Set conditional watchpoint."
+
+gdb_test "info break" \
+         ".*${ws}.*atchpoint${ws}keep${ws}y${ws}thread${ws}.*atchpoint${ws}keep${ws}y${ws}thread${ws}stop only if i = 2" \
+         "Check that watchpoint is set correctly."
+
+# Check for right error when using both 'if' and 'thread' clauses.
+
+gdb_test "break foo.adb:$bp_location if thread = 10 thread 999" \
+         ".*Unknown thread 999\\." \
+         "Combination of 'if' and 'thread' delimiters."
diff --git a/gdb/testsuite/gdb.ada/expr_delims/foo.adb b/gdb/testsuite/gdb.ada/expr_delims/foo.adb
new file mode 100644
index 0000000..8384741
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/expr_delims/foo.adb
@@ -0,0 +1,26 @@
+--  Copyright 2008-2013 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 Ada.Text_IO; use Ada.Text_IO;
+
+procedure Foo is
+   Thread: Integer;
+begin
+   Thread := 0;
+   for I in 1 .. 100 loop
+      Thread := Thread + I; -- STOP_HERE
+   end loop;
+   Put(Integer'Image(Thread));
+end Foo;
-- 
1.7.9.5