[PATCH] Apply substitute-path to relative filenames as well

[LRN]

On 06.03.2019 1:10, Tom Tromey wrote:
> LRN writes:
>> 2019-02-28 Руслан Ижбулатов  <lrn1986@gmail.com>
>> 
>>        * source.c (find_and_open_source): Apply substitute-path to all
>>        filenames, both absolute and relative
> 
> Is it possible to get a test case for the patch?

No. I couldn't find a gdb testcase for the substitute-path feature (there's one
that checks issuing the `set substitute-path` command itself, but it doesn't
seem to be testing its *runtime effect*, i.e. how it is applied when gdb needs
to read a source file), so i can't provide a test case for this change by
modifying an existing one. That means i'd have to write one from scratch, and i
wouldn't know how to even begin to do that.

Also, running gdb testsuite requires dejagnu, which i don't have (and by "i
don't have" i mean "i've never built it from the source", as this is how i get
90% of all my dev software). It should technically be possible for me to build
it, but that'll take time that i would rather spend on other things.

>>    gdb::unique_xmalloc_ptr<char> rewritten_filename;
> [...]
>> +  rewritten_filename = rewrite_source_path (filename);
> 
> I think these two lines can now be joined; no need to have a separate
> assignment.
> 

New version of the patch is attached.
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From 74ec81cb519c331d8b10d419eefa2a599fac2f4e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A0=D1=83=D1=81=D0=BB=D0=B0=D0=BD=20=D0=98=D0=B6=D0=B1?=
 =?UTF-8?q?=D1=83=D0=BB=D0=B0=D1=82=D0=BE=D0=B2?= <lrn1986@gmail.com>
Date: Thu, 28 Feb 2019 10:25:41 +0000
Subject: [PATCH] Apply substitute-path to relative filenames as well

When source file path is relative to the build directory (which
is considered a good practice and is enforced in certain buildsystems,
such as meson), gdb only applies substitute-path to the build directory
path. Then gdb appends the source file path to the rewritten build
directory path, and tries to access that.

This fails if either two of the following conditions are true:
a) The user didn't specify substitute-path for the build directory.
   This is highly likely, since path substitution for build directories
   is not documented anywhere, and since gdb does not tell[0] the user
   the path to the build directory, just the source file path.
b) The source file path changed.
   This can also easily happen, since a source path that is relative
   to the build directory can include any number of directory names
   that are not part of the program source tree (starting with the
   name of the root directory of the source tree). Gdb will not apply
   substitute-path to that relative path, thus there is no way for
   the user to tell gdb about these changes.

This commit changes the code to apply substitute-path to all filenames,
both relative and absolute. This way it is possible to do things like:

set substitute-path ../foobar-1.0 /src/my/foobar-1.0

which is completely in line with the user expectations.

This might break unusual cases where build directory path is also
relative (is that even possible?) and happens to match the path
to the source directory (i.e. happens to match a substitution rule).

[0]: There's a "maintenance info symtabs" command that does show the names
     of the build directories, but normal users are not required to
     know or use that.
---
 gdb/source.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/gdb/source.c b/gdb/source.c
index f99215f..3fc7717 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -1027,16 +1027,10 @@ find_and_open_source (const char *filename,
 	}
     }
 
-  gdb::unique_xmalloc_ptr<char> rewritten_filename;
-  if (IS_ABSOLUTE_PATH (filename))
-    {
-      /* If filename is absolute path, try the source path
-	 substitution on it.  */
-      rewritten_filename = rewrite_source_path (filename);
+  gdb::unique_xmalloc_ptr<char> rewritten_filename = rewrite_source_path (filename);
 
-      if (rewritten_filename != NULL)
-	filename = rewritten_filename.get ();
-    }
+  if (rewritten_filename != NULL)
+    filename = rewritten_filename.get ();
 
   result = openp (path, OPF_SEARCH_IN_PATH | OPF_RETURN_REALPATH, filename,
 		  OPEN_MODE, fullname);
-- 
2.4.0

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