commit 331735a357a73c7b8adc205241ac3cc6543d985e
Author: Felix Fietkau <nbd@openwrt.org>
Date:   Tue Nov 17 12:38:22 2015 +0000

    gcc: add a patch to 5.x that supports translation of __FILE__ paths
    
    Signed-off-by: Felix Fietkau <nbd@openwrt.org>
    
    SVN-Revision: 47490

Forward ported from attachment to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47047

--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -588,6 +588,10 @@ c_common_handle_option (size_t scode, co
       add_path (xstrdup (arg), SYSTEM, 0, true);
       break;
 
+    case OPT_iremap:
+      add_cpp_remap_path (arg);
+      break;
+
     case OPT_iwithprefix:
       add_prefixed_path (arg, SYSTEM);
       break;
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1825,6 +1825,10 @@ iquote
 C ObjC C++ ObjC++ Joined Separate MissingArgError(missing path after %qs)
 -iquote <dir>	Add <dir> to the end of the quote include path.
 
+iremap
+C ObjC C++ ObjC++ Joined Separate
+-iremap <src:dst>  Convert <src> to <dst> if it occurs as prefix in __FILE__.
+
 iwithprefix
 C ObjC C++ ObjC++ Joined Separate
 -iwithprefix <dir>	Add <dir> to the end of the system include path.
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -4272,6 +4272,7 @@ Refer to the GCC manual for full documen
 @c man begin SYNOPSIS
 cpp [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
     [@option{-I}@var{dir}@dots{}] [@option{-iquote}@var{dir}@dots{}]
+    [@option{-iremap}@var{src}:@var{dst}]
     [@option{-M}|@option{-MM}] [@option{-MG}] [@option{-MF} @var{filename}]
     [@option{-MP}] [@option{-MQ} @var{target}@dots{}]
     [@option{-MT} @var{target}@dots{}]
--- a/gcc/doc/cppopts.texi
+++ b/gcc/doc/cppopts.texi
@@ -220,6 +220,12 @@ extensions @samp{.i}, @samp{.ii} or @sam
 extensions that GCC uses for preprocessed files created by
 @option{-save-temps}.
 
+@item -iremap @var{src}:@var{dst}
+@opindex iremap
+Replace the prefix @var{src} in __FILE__ with @var{dst} at expansion time.
+This option can be specified more than once.  Processing stops at the first
+match.
+
 @item -fdirectives-only
 @opindex fdirectives-only
 When preprocessing, handle directives, but do not expand macros.
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -11865,6 +11865,12 @@ by @option{-fplugin=@var{name}} instead
 @option{-fplugin=@var{path}/@var{name}.so}.  This option is not meant
 to be used by the user, but only passed by the driver.
 
+@item -iremap @var{src}:@var{dst}
+@opindex iremap
+Replace the prefix @var{src} in __FILE__ with @var{dst} at expansion time.
+This option can be specified more than once.  Processing stops at the first
+match.
+
 @item -L@var{dir}
 @opindex L
 Add directory @var{dir} to the list of directories to be searched
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -820,6 +820,9 @@ extern void cpp_set_lang (cpp_reader *,
 /* Set the include paths.  */
 extern void cpp_set_include_chains (cpp_reader *, cpp_dir *, cpp_dir *, int);
 
+/* Provide src:dst pair for __FILE__ remapping.  */
+extern void add_cpp_remap_path (const char *);
+
 /* Call these to get pointers to the options, callback, and deps
    structures for a given reader.  These pointers are good until you
    call cpp_finish on that reader.  You can either edit the callbacks
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -227,6 +227,64 @@ static const char * const monthnames[] =
   "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
 };
 
+static size_t remap_pairs;
+static char **remap_src;
+static char **remap_dst;
+
+void
+add_cpp_remap_path (const char *arg)
+{
+  const char *arg_dst;
+  size_t len;
+
+  arg_dst = strchr(arg, ':');
+  if (arg_dst == NULL)
+    {
+      fprintf(stderr, "Invalid argument for -iremap\n");
+      exit(1);
+    }
+
+  len = arg_dst - arg;
+  ++arg_dst;
+
+  remap_src = (char **) xrealloc(remap_src, sizeof(char *) * (remap_pairs + 1));
+  remap_dst = (char **) xrealloc(remap_dst, sizeof(char *) * (remap_pairs + 1));
+
+  remap_src[remap_pairs] = (char *) xmalloc(len + 1);
+  memcpy(remap_src[remap_pairs], arg, len);
+  remap_src[remap_pairs][len] = '\0';
+  remap_dst[remap_pairs] = xstrdup(arg_dst);
+  ++remap_pairs;
+}
+
+static const char *
+cpp_remap_file (const char *arg, char **tmp_name)
+{
+  char *result;
+  size_t i, len;
+
+  for (i = 0; i < remap_pairs; ++i)
+    {
+      len = strlen (remap_src[i]);
+      if (strncmp (remap_src[i], arg, len))
+	continue;
+      if (arg[len] == '\0')
+	return xstrdup (remap_dst[i]);
+      if (arg[len] != '/')
+	continue;
+      arg += len;
+      len = strlen (remap_dst[i]);
+      result = (char *) xmalloc (len + strlen (arg) + 1);
+      memcpy(result, remap_dst[i], len);
+      strcpy(result + len, arg);
+      *tmp_name = result;
+
+      return result;
+    }
+
+   return arg;
+}
+
 /* Helper function for builtin_macro.  Returns the text generated by
    a builtin macro. */
 const uchar *
@@ -290,6 +348,7 @@ _cpp_builtin_macro_text (cpp_reader *pfi
       {
 	unsigned int len;
 	const char *name;
+	char *tmp_name = NULL;
 	uchar *buf;
 	
 	if (node->value.builtin == BT_FILE)
@@ -301,6 +360,7 @@ _cpp_builtin_macro_text (cpp_reader *pfi
 	    if (!name)
 	      abort ();
 	  }
+	name = cpp_remap_file (name, &tmp_name);
 	len = strlen (name);
 	buf = _cpp_unaligned_alloc (pfile, len * 2 + 3);
 	result = buf;
@@ -308,6 +368,7 @@ _cpp_builtin_macro_text (cpp_reader *pfi
 	buf = cpp_quote_string (buf + 1, (const unsigned char *) name, len);
 	*buf++ = '"';
 	*buf = '\0';
+	free (tmp_name);
       }
       break;