Re: [PATCH 1/4] gdb/python: make some global variables static

[Andrew Burgess <aburgess@redhat.com>]

* Enze Li <lienze2010@hotmail.com> [2021-11-25 23:02:49 +0800]:

> Hi Andrew,
> 
> After using this patch, I encountered the following error when
> compiling.
> 
> -----------------------------------------------------------------------
>   CXXLD  gdb
> /usr/lib64/gcc/x86_64-suse-linux/11/../../../../x86_64-suse-
> linux/bin/ld: extension.o: in function `ext_lang_before_prompt(char
> const*)':
> /home/lee/dev/binutils-gdb/gdb/extension.c:914: undefined reference to
> `extension_language_python'
> /usr/lib64/gcc/x86_64-suse-linux/11/../../../../x86_64-suse-
> linux/bin/ld: extension.o: in function
> `get_ext_lang_defn(extension_language)':
> /home/lee/dev/binutils-gdb/gdb/extension.c:107: undefined reference to
> `extension_language_python'
> /usr/lib64/gcc/x86_64-suse-linux/11/../../../../x86_64-suse-
> linux/bin/ld: /home/lee/dev/binutils-gdb/gdb/extension.c:105: undefined
> reference to `extension_language_python'
> /usr/lib64/gcc/x86_64-suse-linux/11/../../../../x86_64-suse-
> linux/bin/ld: extension.o: in function `get_ext_lang_of_file(char
> const*)':
> /home/lee/dev/binutils-gdb/gdb/extension.c:132: undefined reference to
> `extension_language_python'
> /usr/lib64/gcc/x86_64-suse-linux/11/../../../../x86_64-suse-
> linux/bin/ld: extension.o: in function `ext_lang_initialization()':
> /home/lee/dev/binutils-gdb/gdb/extension.c:331: undefined reference to
> `extension_language_python'
> /usr/lib64/gcc/x86_64-suse-linux/11/../../../../x86_64-suse-
> linux/bin/ld: extension.o:/home/lee/dev/binutils-
> gdb/gdb/extension.c:359: more undefined references to
> `extension_language_python' follow
> collect2: error: ld returned 1 exit status
> make[2]: *** [Makefile:1904: gdb] Error 1
> make[2]: Leaving directory '/home/lee/dev/binutils-gdb/gdb'
> make[1]: *** [Makefile:13458: all-gdb] Error 2
> make[1]: Leaving directory '/home/lee/dev/binutils-gdb'
> make: *** [Makefile:1000: all] Error 2
> ----------------------------------------------------------------------
> 
> On Thu, 2021-11-25 at 10:12 +0000, Andrew Burgess via Gdb-patches
> wrote:
> > * Tom Tromey <tom@tromey.com> [2021-10-27 14:20:01 -0600]:
> > 
> > > > > > > > "Andrew" == Andrew Burgess <andrew.burgess@embecosm.com>
> > > > > > > > writes:
> > > 
> > > Andrew> Make a couple of global variables static in python/python.c. 
> > > To do
> > > Andrew> this I had to move the definition of
> > > extension_language_python to
> > > Andrew> later in the file.
> > > 
> > > Andrew> There should be no user visible changes after this commit.
> > > 
> > > This looks good to me.
> > 
> > Thanks, I've pushed this patch.
> > 
> > Andrew
> > 
> 
> Here is my system environment,
> OpenSuse Tumbleweed (Updated just now)
> - gcc 11.2.1 20210816 
> [revision 056e324ce46a7924b5cf10f61010cf9dd2ca10e9]
> 
> I executed the following command to compile，
> # ./configure --prefix=/path/to/gdb-src/build/
> # make
> 
> I guess the problem may be in the macro definition. I tested with the
> following patch and the problem disappeared. Hope this may help to
> solve this problem.
> 
> -----------------------------------------------------------------------
> diff --git a/gdb/python/python.c b/gdb/python/python.c
> index d8a6a5978de..bfb691f0eac 100644
> --- a/gdb/python/python.c
> +++ b/gdb/python/python.c
> @@ -164,6 +164,8 @@ static const struct extension_language_ops
> python_extension_ops =
>    gdbpy_colorize,
>  };
>  
> +#endif /* HAVE_PYTHON */
> +
>  /* The main struct describing GDB's interface to the Python
>     extension language.  */
>  const struct extension_language_defn extension_language_python =
> @@ -186,6 +188,8 @@ const struct extension_language_defn
> extension_language_python =
>  #endif
>  };
>  
> +#ifdef HAVE_PYTHON
> +
>  /* Architecture and language to be used in callbacks from
>     the Python interpreter.  */
>  struct gdbarch *python_gdbarch;
> -----------------------------------------------------------------------

Enze,

Thanks for reporting this, and thanks for looking into the problem and
providing a fix.

I pushed the patch below to resolve this issue.

Thanks,
Andrew

---

commit 9e99facd6cae1a94923166bd02f716d96395c19f
Author: Enze Li <lienze2010@hotmail.com>
Date:   Thu Nov 25 18:05:46 2021 +0000

    gdb: ensure extension_language_python is always defined
    
    In this commit:
    
      commit c6a6aad52d9e839d6a84ac31cabe2b7e1a2a31a0
      Date:   Mon Oct 25 17:25:45 2021 +0100
    
          gdb/python: make some global variables static
    
    building without Python was broken.  The extension_language_python
    global was moved from being always defined, to only being defined when
    the HAVE_PYTHON macro was defined.  As a consequence, building without
    Python support would result in errors like:
    
      /usr/bin/ld: extension.o:(.rodata+0x120): undefined reference to `extension_language_python'
    
    This commit fixes the problem by moving the definition of
    extension_language_python outside of the HAVE_PYTHON macro protection.

diff --git a/gdb/python/python.c b/gdb/python/python.c
index d8a6a5978de..bfb691f0eac 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -164,6 +164,8 @@ static const struct extension_language_ops python_extension_ops =
   gdbpy_colorize,
 };
 
+#endif /* HAVE_PYTHON */
+
 /* The main struct describing GDB's interface to the Python
    extension language.  */
 const struct extension_language_defn extension_language_python =
@@ -186,6 +188,8 @@ const struct extension_language_defn extension_language_python =
 #endif
 };
 
+#ifdef HAVE_PYTHON
+
 /* Architecture and language to be used in callbacks from
    the Python interpreter.  */
 struct gdbarch *python_gdbarch;