[commit/Ada] Use our builtin type when evaluating conditional expressions

[commit/Ada] Use our builtin type when evaluating conditional expressions

[Joel Brobecker]

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This is a problem reported by a customer who was debugging a gigantic
application. I think it was on pa-hpux, but it might have been on
x86-linux, and the target is actually not relevant. We reproduced
the problem with the following command:

    (gdb) p null /= null

It first hangs for a while, and then we get:

    utils.c:1020: internal-error: virtual memory exhausted: can't allocate 4072 bytes.
    A problem internal to GDB has been detected,
    further debugging may prove unreliable.

Jerome Guitton did the investigation and said:

The problem comes from the fact that GDB casts "null /= null" into the
language boolean type (i.e. "standard.boolean"). And it lookups the
boolean type into the debug info of the application. As type boolean
is defined in every compilation unit, every psymtabs matchs; as a
consequence, all the corresponding symtabs are built. This roughly
means that the debugger loads every symbols when evaluating a
conditional expression. As the application is really huge, we run
out of memory before completing the operation.

This problem is avoided by making sure that we use our boolean
builtin type rather than trying to look it up...

2009-03-12  Jerome Guitton  <guitton@adacore.com>

        * language.c (lang_bool_type): Set lai->bool_type_symbol to NULL.

Tested on amd64-linux. Checked in.

-- 
Joel

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diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 0724804..0ec724f 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -11013,7 +11013,7 @@ ada_language_arch_info (struct gdbarch *gdbarch,
   TYPE_NAME (lai->primitive_type_vector [ada_primitive_type_system_address])
     = "system__address";
 
-  lai->bool_type_symbol = "boolean";
+  lai->bool_type_symbol = NULL;
   lai->bool_type_default = builtin->builtin_bool;
 }
 \f

Re: [commit/Ada] Use our builtin type when evaluating conditional expressions

[Tom Tromey]

>>>>> "Joel" == Joel Brobecker <brobecker@adacore.com> writes:

Joel>     (gdb) p null /= null

Jerome> The problem comes from the fact that GDB casts "null /= null"
Jerome> into the language boolean type (i.e. "standard.boolean"). And
Jerome> it lookups the boolean type into the debug info of the
Jerome> application. As type boolean is defined in every compilation
Jerome> unit, every psymtabs matchs; as a consequence, all the
Jerome> corresponding symtabs are built. This roughly means that the
Jerome> debugger loads every symbols when evaluating a conditional
Jerome> expression.

I'm curious whether this will be a problem for any language defining
bool_type_symbol.  If so, perhaps a language-neutral fix could be
found.  If not, what is it that makes this specific to Ada?

Tom

Re: [commit/Ada] Use our builtin type when evaluating conditional expressions

[Joel Brobecker]

> I'm curious whether this will be a problem for any language defining
> bool_type_symbol.  If so, perhaps a language-neutral fix could be
> found.  If not, what is it that makes this specific to Ada?

In most language, the lookup stops at the first match. In Ada,
we have to continue the lookup over all units, in case we have
homonyms. This is why we have treated this as an Ada-specific issue.

-- 
Joel