[PATCH] gdb: fix auto-load variable expansion when path is nontrivial

[PATCH] gdb: fix auto-load variable expansion when path is nontrivial

[Arsen Arsenović]

This fixes the auto-load script-directory default of
"$debugdir:$datadir/auto-load", which has recently stopped trying to
load from the $datadir recently.

Likely broken by 02601231fdd91a7bd4837ce202906ea2ce661489.
---
Evening!

This patch addresses a bug I found in the expansion of the auto-load
path, where only strings equal to auto-load path placeholders would get
expanded, as reported on IRC.

It lacks a test, but I've ran out of time for the evening to figure out
the testsuite with, and so, I am sending the patch in to prevent
duplicate effort, even though it's incomplete.

Have a lovely day!

 gdb/auto-load.c | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/gdb/auto-load.c b/gdb/auto-load.c
index 9d6fabe6bbc..b1e372cf2e4 100644
--- a/gdb/auto-load.c
+++ b/gdb/auto-load.c
@@ -183,19 +183,39 @@ auto_load_expand_dir_vars (const char *string)
 
   for (auto &elt : result)
     {
-      if (strcmp (elt.get (), "$datadir") == 0)
+      struct vd {
+	/* Substitutable variable name.  */
+	const char *name;
+	/* Substitutable variable value.  */
+	const char *value;
+      };
+
+      const vd *sub = nullptr;
+
+      const vd vars[] = {
+	{ "$debugdir", debug_file_directory.c_str () },
+	{ "$datadir", gdb_datadir.c_str () }
+      };
+      for (const auto &var : vars)
 	{
-	  elt = make_unique_xstrdup (gdb_datadir.c_str ());
-	  if (debug_auto_load)
-	    auto_load_debug_printf ("Expanded $datadir to \"%s\".",
-				    gdb_datadir.c_str ());
+	  if (!startswith (elt.get (), var.name))
+	    continue;
+
+	  sub = &var;
+	  break;
 	}
-      else if (strcmp (elt.get (), "$debugdir") == 0)
+
+      if (sub)
 	{
-	  elt = make_unique_xstrdup (debug_file_directory.c_str ());
+	  auto new_elt = xstrprintf ("%s%s",
+				     sub->value,
+				     &elt.get ()[strlen (sub->name)]);
 	  if (debug_auto_load)
-	    auto_load_debug_printf ("Expanded $debugdir to \"%s\".",
-				    debug_file_directory.c_str ());
+	    auto_load_debug_printf ("Expanded %s in \"%s\" to \"%s\".",
+				    sub->name,
+				    elt.get (),
+				    new_elt.get ());
+	  elt = std::move (new_elt);
 	}
     }
 
-- 
2.41.0

Re: [PATCH] gdb: fix auto-load variable expansion when path is nontrivial

[Tom Tromey]

>>>>> "Arsen" == Arsen Arsenović via Gdb-patches <gdb-patches@sourceware.org> writes:

Arsen> This fixes the auto-load script-directory default of
Arsen> "$debugdir:$datadir/auto-load", which has recently stopped trying to
Arsen> load from the $datadir recently.

Arsen> Likely broken by 02601231fdd91a7bd4837ce202906ea2ce661489.

Thanks for the patch.

I'm just going to revert that patch instead.  It was just a cleanup and
turns out to be pretty broken.  We can fix it again later if we want,
next time hopefully with more care.

Sorry about the breakage.

I'll send the reversion momentarily.

Tom

Re: [PATCH] gdb: fix auto-load variable expansion when path is nontrivial

[Arsen Arsenović]

[-- Attachment #1: Type: text/plain, Size: 930 bytes --]

Hi Tom,

Tom Tromey <tromey@adacore.com> writes:

> Thanks for the patch.
>
> I'm just going to revert that patch instead.  It was just a cleanup and
> turns out to be pretty broken.  We can fix it again later if we want,
> next time hopefully with more care.
>
> Sorry about the breakage.
>
> I'll send the reversion momentarily.

And I'll confirm that worked:

  [auto-load] auto_load_expand_dir_vars: Expanded $-variables to
  "/usr/lib/debug:/usr/share/gdb/auto-load".
  [auto-load] auto_load_objfile_script_1: Searching 'set auto-load
  scripts-directory' path "$debugdir:$datadir/auto-load".
  [auto-load] auto_load_objfile_script_1: Attempted file
  "/..../14/libstdc++.so.6.0.33-gdb.scm" does not exist.
  [auto-load] auto_load_objfile_script_1: Attempted file
  "/.../14/libstdc++.so.6.0.33-gdb.scm" does not exist.

Thank you for your promptness!

Have a lovely night.
-- 
Arsen Arsenović

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 381 bytes --]