Re: [PATCH v2] gdb: make "start" breakpoint inferior-specific

[Simon Marchi <simon.marchi@efficios.com>]

On 11/11/22 07:37, Tom de Vries wrote:
> On 11/8/22 22:20, Simon Marchi via Gdb-patches wrote:
>> -      std::string arg = string_printf ("-qualified %s", main_name ());
>> +      std::string arg = string_printf ("-qualified %s if $_inferior == %d", main_name (),
>> +                       current_inferior ()->num);
> 
> Hi,
> 
> it seems ada doesn't like the syntax, we get:
> ...
> (gdb) start ^M
> Error in expression, near `1'.^M
> (gdb) UNTESTED: gdb.ada/start.exp: start failed to land inside the right procedure

Huh, sorry, I missed it because it shows up as UNTESTED, which my CI job
doesn't flag as a failure.

Here's a patch that fixes it in a rather naive way.  Ideally, we would
implement proper inferior-specific breakpoints, but in any case we want
un-break the tests sooner than that.

From 28f370e7dda4fb2f240ed29493416e78ed47f176 Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Fri, 11 Nov 2022 07:58:35 -0500
Subject: [PATCH] gdb: fix start breakpoint expression not working in some
 languages

Commit 0be837be9fb4 ("gdb: make "start" breakpoint inferior-specific")
regresses gdb.ada/start.exp:

    (gdb) start
    Error in expression, near `1'.
    (gdb) UNTESTED: gdb.ada/start.exp: start failed to land inside the right procedure

This is because in Ada, the equality operator is =, not ==.

I checked the other languages supported by GDB, these other languages
use = for equality:

 - Pascal: tests like gdb.pascal/hello.exp are affected too
 - Modula-2: I tried building a Modula-2 hello world using gm2, but it
   seems like the generated DWARF doesn't specify the Modula-2 language
   in the CUs, it's C++ and C, so the selected language isn't
   "modula-2".  But if I manually do "set language modula-2" on a dummy
   program and then "start", I get the same error.

Other languages all use ==.

So, a short term fix would be to use = or == in the expression, based on
the current language.  If this was meant to be permanent, I would
suggest adding something like an "equality_operator" method to
language_defn, that returns the right equality operator for the
language.  But the goal is to replace all this with proper
inferior-specific breakpoints, so I hope all this is temporary.

Change-Id: Id4d38e14a80e6bbbb1ad2b2277f974dd55192969
---
 gdb/infcmd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index bf4a68e3557e..6f83949cc7c0 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -428,8 +428,13 @@ run_command_1 (const char *args, int from_tty, enum run_how run_how)
 	 have proper inferior-specific breakpoint support, in the breakpoint
 	 machinery.  We could then avoid inserting a breakpoint in the program
 	 spaces unrelated to this inferior.  */
-      std::string arg = string_printf ("-qualified %s if $_inferior == %d", main_name (),
-				       current_inferior ()->num);
+      const char *op
+	= ((current_language->la_language == language_ada
+	    || current_language->la_language == language_pascal
+	    || current_language->la_language == language_m2) ? "=" : "==");
+      std::string arg = string_printf
+	("-qualified %s if $_inferior %s %d", main_name (), op,
+	 current_inferior ()->num);
       tbreak_command (arg.c_str (), 0);
     }
 

base-commit: 70b9d05b26e861524d70ee90dcd28cfd77032ddd
-- 
2.38.1