Re: [PATCH] Document that index-cache requires build ID

[Sam James <sam@gentoo.org>]

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Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Thu, 17 Apr 2025 14:06:31 -0300
>> Cc: "Eli Zaretskii (eliz@gnu.org)" <eliz@gnu.org>
>> From: Guinevere Larsen <guinevere@redhat.com>
>> 
>>  From 4dfcd1888e3fc3c5707e3f697268d820679a1c7b Mon Sep 17 00:00:00 2001
>>  From: =?UTF-8?q?Llu=C3=ADs=20Batlle=20i=20Rossell?= <viric@viric.name>
>>  Date: Sun, 6 Apr 2025 13:11:06 +0200
>>  Subject: [PATCH] Document that index-cache requires build ID
>> 
>>  ---
>>   gdb/doc/gdb.texinfo | 2 ++
>>   gdb/dwarf2/read.c   | 4 ++++
>>   2 files changed, 6 insertions(+)
>> 
>>  diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
>>  index e034ac53295..37b65ab72ac 100644
>>  --- a/gdb/doc/gdb.texinfo
>>  +++ b/gdb/doc/gdb.texinfo
>>  @@ -22934,6 +22934,8 @@ Indices only work when using DWARF debugging information, not stabs.
>>   It is possible for @value{GDBN} to automatically save a copy of this index in a
>>   cache on disk and retrieve it from there when loading the same binary in the
>>   future.  This feature can be turned on with @kbd{set index-cache enabled on}.
>>  +Note that the cache will use the ELF build ID to identify the cached indices,
>>  +so files without Build ID will not have their index cached.
>>   The following commands can be used to tweak the behavior of the index cache.
>> 
>> Since there are documentation changes, we need Eli Zaretskii to approve this change. I've CC'd him in this
>> email.
>
> Sorry for missing the original submission.
>
> The patch for gdb.texinfo is okay, but please use "build ID", not
> "Build ID", for the second instance, to be consistent about the
> letter-case.
>
> Reviewed-By: Eli Zaretskii <eliz@gnu.org>

I've gone ahead and taken the liberty to push this as obvious enough,
having run into this again recently. I applied your casing tweak and the
style tweaks from Guinevere.


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From 10b5513e6d9a5a8d72bff272b6f254a3b68abc56 Mon Sep 17 00:00:00 2001
Message-ID: <10b5513e6d9a5a8d72bff272b6f254a3b68abc56.1771693680.git.sam@gentoo.org>
From: =?UTF-8?q?Llu=C3=ADs=20Batlle=20i=20Rossell?= <viric@viric.name>
Date: Sun, 6 Apr 2025 13:11:06 +0200
Subject: [PATCH] Document that index-cache requires build ID

Reviewed-By: Guinevere Larsen <guinevere@redhat.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
---
 gdb/doc/gdb.texinfo | 2 ++
 gdb/dwarf2/read.c   | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 5b99c2b2e23..3b2401117c7 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -23198,6 +23198,8 @@ Indices only work when using DWARF debugging information.
 It is possible for @value{GDBN} to automatically save a copy of this index in a
 cache on disk and retrieve it from there when loading the same binary in the
 future.  This feature can be turned on with @kbd{set index-cache enabled on}.
+Note that the cache will use the ELF build ID to identify the cached indices,
+so files without build ID will not have their index cached.
 The following commands can be used to tweak the behavior of the index cache.
 
 @table @code
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 5f18d5f2e9a..302b137526f 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2302,7 +2302,11 @@ get_gdb_index_contents_from_cache (objfile *obj, dwarf2_per_bfd *dwarf2_per_bfd)
 {
   const bfd_build_id *build_id = build_id_bfd_get (obj->obfd.get ());
   if (build_id == nullptr)
-    return {};
+    {
+      dwarf_read_debug_printf ("Not using index-cache for %s due to missing build-id",
+			       objfile_name (obj));
+      return {};
+    }
 
   return global_index_cache.lookup_gdb_index (build_id,
 					      &dwarf2_per_bfd->index_cache_res);

base-commit: 646982f4295bf0a1e64867606d496c34c9a15a0c
-- 
2.53.0


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