Create new common/pathstuff.[ch]

This commit moves the path manipulation routines found on utils.c to a
new common/pathstuff.c, and updates the Makefile.in's accordingly.
The routines moved are "gdb_realpath", "gdb_realpath_keepfile" and
"gdb_abspath".

This will be needed because gdbserver will have to call "gdb_abspath"
on my next patch, which implements a way to expand the path of the
inferior provided by the user in order to allow specifying just the
binary name when starting gdbserver, like:

  $ gdbserver :1234 a.out

With the recent addition of the startup-with-shell feature on
gdbserver, this scenario doesn't work anymore if the user doesn't have
the current directory listed in the PATH variable.

I had to do a minor adjustment on "gdb_abspath" because we don't have
access to "tilde_expand" on gdbserver, so now the function is using
"gdb_tilde_expand" instead.  Otherwise, the code is the same.

Regression tested on the BuildBot, without regressions.

gdb/ChangeLog:
2018-02-28  Sergio Durigan Junior  <sergiodj@redhat.com>

	* Makefile.in (COMMON_SFILES): Add "common/pathstuff.c".
	(HFILES_NO_SRCDIR): Add "common/pathstuff.h".
	* auto-load.c: Include "common/pathstuff.h".
	* common/common-def.h (current_directory): Move here.
	* common/gdb_tilde_expand.c (gdb_tilde_expand_up): New
	function.
	* common/gdb_tilde_expand.h (gdb_tilde_expand_up): New
	prototype.
	* common/pathstuff.c: New file.
	* common/pathstuff.h: New file.
	* compile/compile.c: Include "common/pathstuff.h".
	* defs.h (current_directory): Move to "common/common-defs.h".
	* dwarf2read.c: Include "common/pathstuff.h".
	* exec.c: Likewise.
	* guile/scm-safe-call.c: Likewise.
	* linux-thread-db.c: Likewise.
	* main.c: Likewise.
	* nto-tdep.c: Likewise.
	* objfiles.c: Likewise.
	* source.c: Likewise.
	* symtab.c: Likewise.
	* utils.c: Include "common/pathstuff.h".
	(gdb_realpath): Move to "common/pathstuff.c".
	(gdb_realpath_keepfile): Likewise.
	(gdb_abspath): Likewise.
	* utils.h (gdb_realpath): Move to "common/pathstuff.h".
	(gdb_realpath_keepfile): Likewise.
	(gdb_abspath): Likewise.

gdb/gdbserver/ChangeLog:
2018-02-28  Sergio Durigan Junior  <sergiodj@redhat.com>

	* Makefile.in (SFILES): Add "$(srcdir)/common/pathstuff.c".
	(OBJS): Add "pathstuff.o".
	* server.c (current_directory): New global variable.
	(captured_main): Initialize "current_directory".

5 files changed, 211 insertions, 0 deletions

diff --git a/gdb/common/common-defs.h b/gdb/common/common-defs.h
index acbc32c..881a4ea 100644
--- a/gdb/common/common-defs.h
+++ b/gdb/common/common-defs.h
@@ -91,4 +91,7 @@
 /* Pull in gdb::unique_xmalloc_ptr.  */
 #include "common/gdb_unique_ptr.h"
 
+/* String containing the current directory (what getwd would return).  */
+extern char *current_directory;
+
 #endif /* COMMON_DEFS_H */
diff --git a/gdb/common/gdb_tilde_expand.c b/gdb/common/gdb_tilde_expand.c
index b4f3714..fcb9796 100644
--- a/gdb/common/gdb_tilde_expand.c
+++ b/gdb/common/gdb_tilde_expand.c
@@ -80,3 +80,16 @@ gdb_tilde_expand (const char *dir)
 
   return expanded_dir;
 }
+
+/* See common/gdb_tilde_expand.h.  */
+
+gdb::unique_xmalloc_ptr<char>
+gdb_tilde_expand_up (const char *dir)
+{
+  gdb_glob glob (dir, GLOB_TILDE_CHECK, NULL);
+
+  gdb_assert (glob.pathc () > 0);
+  /* "glob" may return more than one match to the path provided by the
+     user, but we are only interested in the first match.  */
+  return gdb::unique_xmalloc_ptr<char> (xstrdup (glob.pathv ()[0]));
+}
diff --git a/gdb/common/gdb_tilde_expand.h b/gdb/common/gdb_tilde_expand.h
index d0dfb37..22860d3 100644
--- a/gdb/common/gdb_tilde_expand.h
+++ b/gdb/common/gdb_tilde_expand.h
@@ -24,4 +24,8 @@
    the full path.  */
 extern std::string gdb_tilde_expand (const char *dir);
 
+/* Same as GDB_TILDE_EXPAND, but return the full path as a
+   gdb::unique_xmalloc_ptr<char>.  */
+extern gdb::unique_xmalloc_ptr<char> gdb_tilde_expand_up (const char *dir);
+
 #endif /* ! GDB_TILDE_EXPAND_H */
diff --git a/gdb/common/pathstuff.c b/gdb/common/pathstuff.c
new file mode 100644
index 0000000..02f6e44
--- /dev/null
+++ b/gdb/common/pathstuff.c
@@ -0,0 +1,142 @@
+/* Path manipulation routines for GDB and gdbserver.
+
+   Copyright (C) 1986-2018 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "common-defs.h"
+#include "pathstuff.h"
+#include "host-defs.h"
+#include "filenames.h"
+#include "gdb_tilde_expand.h"
+
+/* See common/pathstuff.h.  */
+
+gdb::unique_xmalloc_ptr<char>
+gdb_realpath (const char *filename)
+{
+/* On most hosts, we rely on canonicalize_file_name to compute
+   the FILENAME's realpath.
+
+   But the situation is slightly more complex on Windows, due to some
+   versions of GCC which were reported to generate paths where
+   backlashes (the directory separator) were doubled.  For instance:
+      c:\\some\\double\\slashes\\dir
+   ... instead of ...
+      c:\some\double\slashes\dir
+   Those double-slashes were getting in the way when comparing paths,
+   for instance when trying to insert a breakpoint as follow:
+      (gdb) b c:/some/double/slashes/dir/foo.c:4
+      No source file named c:/some/double/slashes/dir/foo.c:4.
+      (gdb) b c:\some\double\slashes\dir\foo.c:4
+      No source file named c:\some\double\slashes\dir\foo.c:4.
+   To prevent this from happening, we need this function to always
+   strip those extra backslashes.  While canonicalize_file_name does
+   perform this simplification, it only works when the path is valid.
+   Since the simplification would be useful even if the path is not
+   valid (one can always set a breakpoint on a file, even if the file
+   does not exist locally), we rely instead on GetFullPathName to
+   perform the canonicalization.  */
+
+#if defined (_WIN32)
+  {
+    char buf[MAX_PATH];
+    DWORD len = GetFullPathName (filename, MAX_PATH, buf, NULL);
+
+    /* The file system is case-insensitive but case-preserving.
+       So it is important we do not lowercase the path.  Otherwise,
+       we might not be able to display the original casing in a given
+       path.  */
+    if (len > 0 && len < MAX_PATH)
+      return gdb::unique_xmalloc_ptr<char> (xstrdup (buf));
+  }
+#else
+  {
+    char *rp = canonicalize_file_name (filename);
+
+    if (rp != NULL)
+      return gdb::unique_xmalloc_ptr<char> (rp);
+  }
+#endif
+
+  /* This system is a lost cause, just dup the buffer.  */
+  return gdb::unique_xmalloc_ptr<char> (xstrdup (filename));
+}
+
+/* See common/pathstuff.h.  */
+
+gdb::unique_xmalloc_ptr<char>
+gdb_realpath_keepfile (const char *filename)
+{
+  const char *base_name = lbasename (filename);
+  char *dir_name;
+  char *result;
+
+  /* Extract the basename of filename, and return immediately
+     a copy of filename if it does not contain any directory prefix.  */
+  if (base_name == filename)
+    return gdb::unique_xmalloc_ptr<char> (xstrdup (filename));
+
+  dir_name = (char *) alloca ((size_t) (base_name - filename + 2));
+  /* Allocate enough space to store the dir_name + plus one extra
+     character sometimes needed under Windows (see below), and
+     then the closing \000 character.  */
+  strncpy (dir_name, filename, base_name - filename);
+  dir_name[base_name - filename] = '\000';
+
+#ifdef HAVE_DOS_BASED_FILE_SYSTEM
+  /* We need to be careful when filename is of the form 'd:foo', which
+     is equivalent of d:./foo, which is totally different from d:/foo.  */
+  if (strlen (dir_name) == 2 && isalpha (dir_name[0]) && dir_name[1] == ':')
+    {
+      dir_name[2] = '.';
+      dir_name[3] = '\000';
+    }
+#endif
+
+  /* Canonicalize the directory prefix, and build the resulting
+     filename.  If the dirname realpath already contains an ending
+     directory separator, avoid doubling it.  */
+  gdb::unique_xmalloc_ptr<char> path_storage = gdb_realpath (dir_name);
+  const char *real_path = path_storage.get ();
+  if (IS_DIR_SEPARATOR (real_path[strlen (real_path) - 1]))
+    result = concat (real_path, base_name, (char *) NULL);
+  else
+    result = concat (real_path, SLASH_STRING, base_name, (char *) NULL);
+
+  return gdb::unique_xmalloc_ptr<char> (result);
+}
+
+/* See common/pathstuff.h.  */
+
+gdb::unique_xmalloc_ptr<char>
+gdb_abspath (const char *path)
+{
+  gdb_assert (path != NULL && path[0] != '\0');
+
+  if (path[0] == '~')
+    return gdb_tilde_expand_up (path);
+
+  if (IS_ABSOLUTE_PATH (path))
+    return gdb::unique_xmalloc_ptr<char> (xstrdup (path));
+
+  /* Beware the // my son, the Emacs barfs, the botch that catch...  */
+  return gdb::unique_xmalloc_ptr<char>
+    (concat (current_directory,
+	     IS_DIR_SEPARATOR (current_directory[strlen (current_directory) - 1])
+	     ? "" : SLASH_STRING,
+	     path, (char *) NULL));
+}
diff --git a/gdb/common/pathstuff.h b/gdb/common/pathstuff.h
new file mode 100644
index 0000000..3cb02c8
--- /dev/null
+++ b/gdb/common/pathstuff.h
@@ -0,0 +1,49 @@
+/* Path manipulation routines for GDB and gdbserver.
+
+   Copyright (C) 1986-2018 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef PATHSTUFF_H
+#define PATHSTUFF_H
+
+/* Path utilities.  */
+
+/* Return the real path of FILENAME, expanding all the symbolic links.
+
+   Contrary to "gdb_abspath", this function does not use
+   CURRENT_DIRECTORY for path expansion.  Instead, it relies on the
+   current working directory (CWD) of GDB or gdbserver.  */
+
+extern gdb::unique_xmalloc_ptr<char> gdb_realpath (const char *filename);
+
+/* Return a copy of FILENAME, with its directory prefix canonicalized
+   by gdb_realpath.  */
+
+extern gdb::unique_xmalloc_ptr<char>
+  gdb_realpath_keepfile (const char *filename);
+
+/* Return PATH in absolute form, performing tilde-expansion if necessary.
+   PATH cannot be NULL or the empty string.
+   This does not resolve symlinks however, use gdb_realpath for that.
+
+   Contrary to "gdb_realpath", this function uses CURRENT_DIRECTORY
+   for the path expansion.  This may lead to scenarios the current
+   working directory (CWD) is different than CURRENT_DIRECTORY.  */
+
+extern gdb::unique_xmalloc_ptr<char> gdb_abspath (const char *path);
+
+#endif /* PATHSTUFF_H */