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expressions with C preprocessor macro info
- From: Pedro Alves <pedro at codesourcery dot com>
- To: gdb-patches at sourceware dot org
- Date: Sat, 3 May 2008 21:19:27 +0100
- Subject: expressions with C preprocessor macro info
Hi,
I noticed while doing something else in parse.c, something suspicous.
It happens that after preprocessor macros support went
in, parse.c:parse_exp_in_context got changed in a form that
introduced a bug here:
static struct expression *
parse_exp_in_context (char **stringptr, struct block *block, int comma,
int void_context_p)
{
...
if (!block)
block = get_selected_block (&expression_context_pc);
^^^ if this returns a block, expression_context_pc contains
an accurate pc.
/* Fall back to using the current source static context, if any. */
if (!block)
{
struct symtab_and_line cursal = get_current_source_symtab_and_line ();
if (cursal.symtab)
block = BLOCKVECTOR_BLOCK (BLOCKVECTOR (cursal.symtab), STATIC_BLOCK);
}
/* Save the context, if specified by caller, or found above. */
if (block)
{
expression_context_block = block;
expression_context_pc = BLOCK_START (block);
^^^ but here we're always overriding it with BLOCK_START.
}
Talking about this with Jim Blandy, he explained it like so:
"We want the exact PC because macros are scoped from one line to the
next, not by block. ÂFor example, we could have:
  {
   int foo;
   f ();
#define M slurgh;
   g ();
#undef M
   h ();
  }
In this case, there will be only one lexical block covering the
declaration of foo and all three statements, but we'd like to see the
definition of M when we're stopped at the call to g, and not when
we're stopped at the calls to f or h. ÂSo we need to take a PC, find
the source line and file, and then use that to decide whether any
given macro is in scope."
Currently, "print M" when stopped at the g (); call above prints:
(gdb) print M
No symbol "M" in current context.
The attached patch fixes the issue, and adds a test to ensure
we don't regress again.
Tested on x86_64-unknown-linux-pc.
OK?
--
Pedro Alves
2008-05-03 Pedro Alves <pedro@codesourcery.com>
gdb/
* parse.c (parse_exp_in_context): Don't override
expression_context_pc if get_selected_block returned a valid block.
gdb/testsuite/
* gdb.base/macscp.exp, gdb.base/macscp1.c: Add test for printing
expressions with macros.
---
gdb/parse.c | 26 ++++++++++++--------------
gdb/testsuite/gdb.base/macscp.exp | 23 +++++++++++++++++++++++
gdb/testsuite/gdb.base/macscp1.c | 13 +++++++++++++
3 files changed, 48 insertions(+), 14 deletions(-)
Index: src/gdb/parse.c
===================================================================
--- src.orig/gdb/parse.c 2008-05-03 20:32:38.000000000 +0100
+++ src/gdb/parse.c 2008-05-03 20:43:01.000000000 +0100
@@ -961,26 +961,24 @@ parse_exp_in_context (char **stringptr,
old_chain = make_cleanup (free_funcalls, 0 /*ignore*/);
funcall_chain = 0;
- /* If no context specified, try using the current frame, if any. */
+ expression_context_block = block;
- if (!block)
- block = get_selected_block (&expression_context_pc);
+ /* If no context specified, try using the current frame, if any. */
+ if (!expression_context_block)
+ expression_context_block = get_selected_block (&expression_context_pc);
+ else
+ expression_context_pc = BLOCK_START (expression_context_block);
- /* Fall back to using the current source static context, if any. */
+ /* Fall back to using the current source static context, if any. */
- if (!block)
+ if (!expression_context_block)
{
struct symtab_and_line cursal = get_current_source_symtab_and_line ();
if (cursal.symtab)
- block = BLOCKVECTOR_BLOCK (BLOCKVECTOR (cursal.symtab), STATIC_BLOCK);
- }
-
- /* Save the context, if specified by caller, or found above. */
-
- if (block)
- {
- expression_context_block = block;
- expression_context_pc = BLOCK_START (block);
+ expression_context_block
+ = BLOCKVECTOR_BLOCK (BLOCKVECTOR (cursal.symtab), STATIC_BLOCK);
+ if (expression_context_block)
+ expression_context_pc = BLOCK_START (expression_context_block);
}
expout_size = 10;
Index: src/gdb/testsuite/gdb.base/macscp.exp
===================================================================
--- src.orig/gdb/testsuite/gdb.base/macscp.exp 2008-05-03 20:32:39.000000000 +0100
+++ src/gdb/testsuite/gdb.base/macscp.exp 2008-05-03 20:37:56.000000000 +0100
@@ -24,6 +24,7 @@ if $tracelevel then {
set prms_id 0
set bug_id 0
+set srcfile macscp1.c
set testfile "macscp"
set binfile ${objdir}/${subdir}/${testfile}
@@ -405,3 +406,25 @@ for {set i 0} {$i < [llength $funcs]} {i
}
}
}
+
+gdb_test "break [gdb_get_line_number "set breakpoint here"]" \
+ "Breakpoint.*at.* file .*, line.*" \
+ "breakpoint macscp_expr"
+
+gdb_test "continue" "foo = 0;.*" "continue to macsp_expr"
+
+gdb_test "print M" \
+ "No symbol \"M\" in current context\." \
+ "print expression with macro before define."
+
+gdb_test "next" "foo = 1;" "next to definition"
+
+gdb_test "print M" \
+ " = 0" \
+ "print expression with macro in scope."
+
+gdb_test "next" "foo = 2;" "next to definition"
+
+gdb_test "print M" \
+ "No symbol \"M\" in current context\." \
+ "print expression with macro after undef."
Index: src/gdb/testsuite/gdb.base/macscp1.c
===================================================================
--- src.orig/gdb/testsuite/gdb.base/macscp1.c 2008-05-03 20:32:39.000000000 +0100
+++ src/gdb/testsuite/gdb.base/macscp1.c 2008-05-03 20:37:56.000000000 +0100
@@ -63,6 +63,18 @@ macscp1_3 ()
puts ("macscp1_3");
}
+void
+macscp_expr (void)
+{
+ int foo = -1;
+
+ foo = 0; /* set breakpoint here */
+#define M foo
+ foo = 1;
+#undef M
+ foo = 2;
+}
+
int
main (int argc, char **argv)
{
@@ -77,4 +89,5 @@ main (int argc, char **argv)
macscp4_2_from_macscp3 ();
macscp3_2 ();
macscp1_3 ();
+ macscp_expr ();
}