Re: [PATCH v2 3/5] Introduce gdb_chdir

[Sergio Durigan Junior <sergiodj@redhat.com>]

On Wednesday, September 20 2017, Pedro Alves wrote:

> On 09/19/2017 05:28 AM, Sergio Durigan Junior wrote:
>> In order to be able to change the inferior's directory before its
>> execution, it is necessary to perform a tilde expansion of the
>> directory provided by the user and then chdir into the resulting dir.
>> This is what gdb_chdir does.
>> 
>> Unfortunately it is not possible to use "tilde_expand" from readline
>> because this is common code and gdbserver doesn't use readline.  For
>> that reason I decided to go with "glob" and its GNU extension,
>> GLOB_TILDE.  With the import of the "glob" module from gnulib, this is
>> a no-brainer.
>> 
>> gdb/ChangeLog:
>> yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>
>> 
>> 	* Makefile.in (SFILES): Add gdb_chdir.c.
>> 	(HFILES_NO_SRCDIR): Add gdb_chdir.h.
>> 	(COMMON_OBS): Add gdb_chdir.o.
>> 	* cli/cli-cmds.c: Include "gdb_chdir.h".
>> 	(cd_command): Use "gdb_chdir" instead of "tilde_expand
>> 	plus chdir".
>> 	* common/gdb_chdir.c: New file.
>> 	* common/gdb_chdir.h: Likewise.
>> 
>> gdb/gdbserver/ChangeLog:
>> yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>
>> 
>> 	* Makefile.in (SFILES): Add $(srcdir)/common/gdb_chdir.c.
>> 	(OBS): Add gdb_chdir.o.
>> ---
>>  gdb/Makefile.in           |  3 ++
>>  gdb/cli/cli-cmds.c        | 20 +++++-----
>>  gdb/common/gdb_chdir.c    | 96 +++++++++++++++++++++++++++++++++++++++++++++++
>>  gdb/common/gdb_chdir.h    | 26 +++++++++++++
>>  gdb/gdbserver/Makefile.in |  2 +
>>  5 files changed, 136 insertions(+), 11 deletions(-)
>>  create mode 100644 gdb/common/gdb_chdir.c
>>  create mode 100644 gdb/common/gdb_chdir.h
>> 
>> diff --git a/gdb/Makefile.in b/gdb/Makefile.in
>> index 9dfc117b2f..1f093e6c0f 100644
>> --- a/gdb/Makefile.in
>> +++ b/gdb/Makefile.in
>> @@ -1245,6 +1245,7 @@ SFILES = \
>>  	common/filestuff.c \
>>  	common/format.c \
>>  	common/job-control.c \
>> +	common/gdb_chdir.c \
>>  	common/gdb_vecs.c \
>>  	common/new-op.c \
>>  	common/print-utils.c \
>> @@ -1529,6 +1530,7 @@ HFILES_NO_SRCDIR = \
>>  	common/fileio.h \
>>  	common/format.h \
>>  	common/gdb_assert.h \
>> +	common/gdb_chdir.h \
>>  	common/gdb_locale.h \
>>  	common/gdb_setjmp.h \
>>  	common/gdb_signals.h \
>> @@ -1734,6 +1736,7 @@ COMMON_OBS = $(DEPFILES) $(CONFIG_OBS) $(YYOBJ) \
>>  	frame-unwind.o \
>>  	gcore.o \
>>  	gdb_bfd.o \
>> +	gdb_chdir.o \
>>  	gdb-dlfcn.o \
>>  	gdb_obstack.o \
>>  	gdb_regex.o \
>> diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
>> index 85d6d21113..653dd56a64 100644
>> --- a/gdb/cli/cli-cmds.c
>> +++ b/gdb/cli/cli-cmds.c
>> @@ -54,6 +54,8 @@
>>  #include "tui/tui.h"	/* For tui_active et.al.  */
>>  #endif
>>  
>> +#include "gdb_chdir.h"
>> +
>>  #include <fcntl.h>
>>  #include <algorithm>
>>  #include <string>
>> @@ -408,12 +410,7 @@ cd_command (char *dir, int from_tty)
>>       repeat might be useful but is more likely to be a mistake.  */
>>    dont_repeat ();
>>  
>> -  gdb::unique_xmalloc_ptr<char> dir_holder
>> -    (tilde_expand (dir != NULL ? dir : "~"));
>> -  dir = dir_holder.get ();
>> -
>> -  if (chdir (dir) < 0)
>> -    perror_with_name (dir);
>> +  gdb_chdir (dir != NULL ? dir : "~");
>>  
>>  #ifdef HAVE_DOS_BASED_FILE_SYSTEM
>>    /* There's too much mess with DOSish names like "d:", "d:.",
>> @@ -436,20 +433,21 @@ cd_command (char *dir, int from_tty)
>>  	len--;
>>      }
>>  
>> -  dir_holder.reset (savestring (dir, len));
>> -  if (IS_ABSOLUTE_PATH (dir_holder.get ()))
>> +  std::string newdir = std::string (dir, len);
>> +  const char *newdir_str = newdir.c_str ();
>> +  if (IS_ABSOLUTE_PATH (newdir_str))
>>      {
>>        xfree (current_directory);
>> -      current_directory = dir_holder.release ();
>> +      current_directory = xstrdup (newdir_str);
>
> This introduces one extra deep string dup.  One to
> construct the std::string, and another here in this xstrdup.
>
> How about simply, above:
>
>  -  dir_holder.reset (savestring (dir, len));
>  +  gdb::unique_xmalloc_ptr<char> dir_holder (savestring (dir, len))
>
>
> But more importantly, isn't there a behavior change here?
> Before, current_directory would be a copy of the the expand
> path, while after the patch, it's a copy of the input string,
> before expansion.  Right?

Wow, you're right.  I am sorry about letting this slip.  I guess I made
so many modifications to this code that in the end I forgot that "dir"
wasn't being updated to hold the expanded path anymore.  I will fix
this.

And with your review of patch #4, it is clear that we don't need
a gdb_chdir; we need a gdb_tilde_expand.  Therefore I will make the
necessary modifications to export that function instead.

>
>>      }
>>    else
>>      {
>>        if (IS_DIR_SEPARATOR (current_directory[strlen (current_directory) - 1]))
>> -	current_directory = concat (current_directory, dir_holder.get (),
>> +	current_directory = concat (current_directory, newdir_str,
>>  				    (char *) NULL);
>>        else
>>  	current_directory = concat (current_directory, SLASH_STRING,
>> -				    dir_holder.get (), (char *) NULL);
>> +				    newdir_str, (char *) NULL);
>>      }
>
>
>> +  /* Destroy the object and free M_GLOB.  */
>> +  ~gdb_glob ()
>> +  {
>> +    globfree (&m_glob);
>> +  }
>> +
>> +  /* Return the GL_PATHC component of M_GLOB.  */
>> +  int
>> +  pathc () const
>> +  {
>> +    return m_glob.gl_pathc;
>> +  }
>
> We've been putting type and function name in the
> same line in inline member functions.  That's the
> de facto standard in GCC as well, AFAICS.

Done.

>
>> +
>> +  /* Return the GL_PATHV component of M_GLOB.  */
>> +  char **
>> +  pathv () const
>> +  {
>> +    return m_glob.gl_pathv;
>> +  }
>
> Ditto.

Done.

>
>> +#ifndef HAVE_GDB_CHDIR_H
>> +#define HAVE_GDB_CHDIR_H
>> +
>> +/* Perform a "chdir" to DIR, doing the proper tilde expansion before.  */
>> +extern void gdb_chdir (const char *dir);
>
> Nit, I'd drop "the proper", as it doesn't see to add value.
> I.e., what's proper and what's not proper?

Done.

Thanks,

-- 
Sergio
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