From 1bfd15d4f07f7d76ec399b1a45bc16c404f1465a Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Mon, 6 Nov 2017 07:35:24 +0100
Subject: [PATCH] backport build path prefix map. WIP

---
 gcc/c-family/c-common.c                            |  20 ++
 gcc/c-family/c-common.h                            |   5 +
 gcc/c-family/c-lex.c                               |   1 +
 gcc/cp/cfns.gperf                                  |   2 +-
 gcc/debug.h                                        |   1 +
 gcc/final.c                                        |  54 +++--
 gcc/opts-global.c                                  |   2 +
 gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-1.c |  11 +
 gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-2.c |  12 ++
 .../gcc.dg/debug/dwarf2/build_path_prefix_map-1.c  |   9 +
 .../gcc.dg/debug/dwarf2/build_path_prefix_map-2.c  |   8 +
 include/prefix-map.h                               | 108 ++++++++++
 libcpp/include/cpplib.h                            |   3 +
 libcpp/init.c                                      |   3 +
 libcpp/internal.h                                  |   5 +
 libcpp/macro.c                                     |  16 ++
 libiberty/Makefile.in                              |  14 +-
 libiberty/prefix-map.c                             | 226 +++++++++++++++++++++
 18 files changed, 467 insertions(+), 33 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-1.c
 create mode 100644 gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-2.c
 create mode 100644 gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-1.c
 create mode 100644 gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-2.c
 create mode 100644 include/prefix-map.h
 create mode 100644 libiberty/prefix-map.c

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 82a2b8d6c..b4ca42b73 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -21,6 +21,7 @@ along with GCC; see the file COPYING3.  If not see
 
 #include "config.h"
 #include "system.h"
+#include "prefix-map.h"
 #include "coretypes.h"
 #include "tm.h"
 #include "intl.h"
@@ -10736,4 +10737,23 @@ build_userdef_literal (tree suffix_id, tree value, tree num_string)
   return literal;
 }
 
+/* Read BUILD_PATH_PREFIX_MAP from environment to have deterministic relative
+   paths to replace embedded absolute paths to get reproducible results.
+   Returns NULL if BUILD_PATH_PREFIX_MAP is badly formed.  */
+
+struct prefix_map **
+cb_get_build_path_prefix_map (cpp_reader *pfile ATTRIBUTE_UNUSED)
+{
+  struct prefix_map **map = XCNEW (struct prefix_map *);
+
+  const char *arg = getenv ("BUILD_PATH_PREFIX_MAP");
+  if (!arg || prefix_map_parse (map, arg))
+    return map;
+
+  free (map);
+  error_at (input_location, "environment variable BUILD_PATH_PREFIX_MAP is "
+	    "not well formed; see the GCC documentation for more details.");
+  return NULL;
+}
+
 #include "gt-c-family-c-common.h"
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 835b13bbc..7591bd6b0 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1116,4 +1116,9 @@ struct GTY(()) tree_userdef_literal {
 
 extern tree build_userdef_literal (tree suffix_id, tree value, tree num_string);
 
+/* Read BUILD_PATH_PREFIX_MAP from environment to have deterministic relative
+   paths to replace embedded absolute paths to get reproducible results.
+   Returns NULL if BUILD_PATH_PREFIX_MAP is badly formed.  */
+extern struct prefix_map **cb_get_build_path_prefix_map (cpp_reader *pfile);
+
 #endif /* ! GCC_C_COMMON_H */
diff --git a/gcc/c-family/c-lex.c b/gcc/c-family/c-lex.c
index 7e2029ce0..8cef0f2a8 100644
--- a/gcc/c-family/c-lex.c
+++ b/gcc/c-family/c-lex.c
@@ -84,6 +84,7 @@ init_c_lex (void)
   cb->def_pragma = cb_def_pragma;
   cb->valid_pch = c_common_valid_pch;
   cb->read_pch = c_common_read_pch;
+  cb->get_build_path_prefix_map = cb_get_build_path_prefix_map;
 
   /* Set the debug callbacks if we can use them.  */
   if ((debug_info_level == DINFO_LEVEL_VERBOSE
diff --git a/gcc/cp/cfns.gperf b/gcc/cp/cfns.gperf
index ba0c487a6..0f9a79ac7 100644
--- a/gcc/cp/cfns.gperf
+++ b/gcc/cp/cfns.gperf
@@ -26,7 +26,7 @@ __inline
 __attribute__ ((__gnu_inline__))
 #endif
 #endif
-const char * libc_name_p (const char *, unsigned int);
+inline const char * libc_name_p (const char *, unsigned int);
 %}
 %%
 # The standard C library functions, for feeding to gperf; the result is used
diff --git a/gcc/debug.h b/gcc/debug.h
index 828ede230..1f9a69e56 100644
--- a/gcc/debug.h
+++ b/gcc/debug.h
@@ -187,6 +187,7 @@ extern void dwarf2out_switch_text_section (void);
 
 const char *remap_debug_filename (const char *);
 void add_debug_prefix_map (const char *);
+void add_debug_prefix_map_from_envvar ();
 
 /* For -fdump-go-spec.  */
 
diff --git a/gcc/final.c b/gcc/final.c
index 718caf154..d72dec2e5 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -48,6 +48,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
+#include "prefix-map.h"
 #include "tm.h"
 
 #include "tree.h"
@@ -1435,22 +1436,9 @@ asm_str_count (const char *templ)
   return count;
 }
 \f
-/* ??? This is probably the wrong place for these.  */
-/* Structure recording the mapping from source file and directory
-   names at compile time to those to be embedded in debug
-   information.  */
-typedef struct debug_prefix_map
-{
-  const char *old_prefix;
-  const char *new_prefix;
-  size_t old_len;
-  size_t new_len;
-  struct debug_prefix_map *next;
-} debug_prefix_map;
-
-/* Linked list of such structures.  */
-debug_prefix_map *debug_prefix_maps;
 
+/* Linked list of `struct prefix_map'.  */
+static struct prefix_map *debug_prefix_maps = NULL;
 
 /* Record a debug file prefix mapping.  ARG is the argument to
    -fdebug-prefix-map and must be of the form OLD=NEW.  */
@@ -1458,7 +1446,7 @@ debug_prefix_map *debug_prefix_maps;
 void
 add_debug_prefix_map (const char *arg)
 {
-  debug_prefix_map *map;
+  struct prefix_map *map;
   const char *p;
 
   p = strchr (arg, '=');
@@ -1467,7 +1455,7 @@ add_debug_prefix_map (const char *arg)
       error ("invalid argument %qs to -fdebug-prefix-map", arg);
       return;
     }
-  map = XNEW (debug_prefix_map);
+  map = XNEW (struct prefix_map);
   map->old_prefix = xstrndup (arg, p - arg);
   map->old_len = p - arg;
   p++;
@@ -1477,28 +1465,32 @@ add_debug_prefix_map (const char *arg)
   debug_prefix_maps = map;
 }
 
+/* Add debug-prefix-maps from BUILD_PATH_PREFIX_MAP environment variable.  */
+
+void
+add_debug_prefix_map_from_envvar ()
+{
+  const char *arg = getenv ("BUILD_PATH_PREFIX_MAP");
+
+  if (!arg || prefix_map_parse (&debug_prefix_maps, arg))
+    return;
+
+  error ("environment variable BUILD_PATH_PREFIX_MAP is "
+	 "not well formed; see the GCC documentation for more details.");
+}
+
 /* Perform user-specified mapping of debug filename prefixes.  Return
    the new name corresponding to FILENAME.  */
 
 const char *
 remap_debug_filename (const char *filename)
 {
-  debug_prefix_map *map;
-  char *s;
-  const char *name;
-  size_t name_len;
+  const char *name = prefix_map_remap_alloca (debug_prefix_maps, filename);
 
-  for (map = debug_prefix_maps; map; map = map->next)
-    if (filename_ncmp (filename, map->old_prefix, map->old_len) == 0)
-      break;
-  if (!map)
+  if (name == filename)
     return filename;
-  name = filename + map->old_len;
-  name_len = strlen (name) + 1;
-  s = (char *) alloca (name_len + map->new_len);
-  memcpy (s, map->new_prefix, map->new_len);
-  memcpy (s + map->new_len, name, name_len);
-  return ggc_strdup (s);
+
+  return ggc_strdup (name);
 }
 \f
 /* Return true if DWARF2 debug info can be emitted for DECL.  */
diff --git a/gcc/opts-global.c b/gcc/opts-global.c
index b93d56fcd..f3c653bc1 100644
--- a/gcc/opts-global.c
+++ b/gcc/opts-global.c
@@ -322,6 +322,8 @@ handle_common_deferred_options (void)
   if (flag_dump_all_passed)
     enable_rtl_dump_file ();
 
+  add_debug_prefix_map_from_envvar ();
+
   FOR_EACH_VEC_ELT (cl_deferred_option, vec, i, opt)
     {
       switch (opt->opt_index)
diff --git a/gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-1.c b/gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-1.c
new file mode 100644
index 000000000..960503813
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-1.c
@@ -0,0 +1,11 @@
+/* __FILE__ should strip BUILD_PATH_PREFIX_MAP if the latter is a prefix. */
+/* { dg-do run } */
+/* { dg-set-compiler-env-var BUILD_PATH_PREFIX_MAP "MACROTEST=$srcdir" } */
+
+int
+main ()
+{
+  if (__builtin_strcmp (__FILE__, "MACROTEST/gcc.dg/cpp/build_path_prefix_map-1.c") != 0)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-2.c b/gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-2.c
new file mode 100644
index 000000000..4b0aacd5e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/build_path_prefix_map-2.c
@@ -0,0 +1,12 @@
+/* __FILE__ should not be relative if BUILD_PATH_PREFIX_MAP is not set, and gcc is
+   asked to compile an absolute filename as is the case with this test.  */
+/* { dg-do run } */
+/* { dg-set-compiler-env-var BUILD_PATH_PREFIX_MAP } */
+
+int
+main ()
+{
+  if (__builtin_strcmp (__FILE__, "./gcc.dg/cpp/build_path_prefix_map-2.c") == 0)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-1.c b/gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-1.c
new file mode 100644
index 000000000..af2b0ed33
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-1.c
@@ -0,0 +1,9 @@
+/* DW_AT_comp_dir should be relative if BUILD_PATH_PREFIX_MAP is a prefix of it.  */
+/* { dg-do compile } */
+/* { dg-options "-gdwarf -dA" } */
+/* { dg-set-compiler-env-var BUILD_PATH_PREFIX_MAP "DWARF2TEST=[file dirname [pwd]]" } */
+/* { dg-final { scan-assembler "DW_AT_comp_dir: \"DWARF2TEST/gcc" } } */
+
+void func (void)
+{
+}
diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-2.c b/gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-2.c
new file mode 100644
index 000000000..4c66bf521
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/dwarf2/build_path_prefix_map-2.c
@@ -0,0 +1,8 @@
+/* DW_AT_comp_dir should be absolute if BUILD_PATH_PREFIX_MAP is not set.  */
+/* { dg-do compile } */
+/* { dg-options "-gdwarf -dA" } */
+/* { dg-final { scan-assembler "DW_AT_comp_dir: \"/" } } */
+
+void func (void)
+{
+}
diff --git a/include/prefix-map.h b/include/prefix-map.h
new file mode 100644
index 000000000..f8edb547e
--- /dev/null
+++ b/include/prefix-map.h
@@ -0,0 +1,108 @@
+/* Declarations for manipulating filename prefixes.
+
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+   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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#ifndef _PREFIX_MAP_H
+#define _PREFIX_MAP_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
+
+/* Linked-list of mappings from old prefixes to new prefixes.  */
+
+struct prefix_map
+{
+  const char *old_prefix;
+  const char *new_prefix;
+  size_t old_len;
+  size_t new_len;
+  struct prefix_map *next;
+};
+
+
+/* Find a mapping suitable for the given OLD_NAME in the linked list MAP.\
+
+   If a mapping is found, writes a pointer to the non-matching suffix part of
+   OLD_NAME in SUFFIX, and its length in SUF_LEN.
+
+   Returns NULL if there was no suitable mapping.  */
+struct prefix_map *
+prefix_map_find (struct prefix_map *map, const char *old_name,
+		 const char **suffix, size_t *suf_len);
+
+/* Prepend a prefix map before a given SUFFIX.
+
+   The remapped name is written to NEW_NAME and returned as a const pointer. No
+   allocations are performed; the caller must ensure it can hold at least
+   MAP->NEW_LEN + SUF_LEN + 1 characters.  */
+const char *
+prefix_map_prepend (struct prefix_map *map, char *new_name,
+		    const char *suffix, size_t suf_len);
+
+/* Remap a filename.
+
+   Returns OLD_NAME unchanged if there was no remapping, otherwise returns a
+   pointer to newly-allocated memory for the remapped filename.  The memory is
+   allocated by the given ALLOC function, which also determines who is
+   responsible for freeing it.  */
+#define prefix_map_remap_alloc_(map_head, old_name, alloc)		       \
+  __extension__								       \
+  ({									       \
+    const char *__suffix;						       \
+    size_t __suf_len;							       \
+    struct prefix_map *__map;						       \
+    (__map = prefix_map_find ((map_head), (old_name), &__suffix, &__suf_len))  \
+      ? prefix_map_prepend (__map,					       \
+			    (char *) alloc (__map->new_len + __suf_len + 1),   \
+			    __suffix, __suf_len)			       \
+      : (old_name);							       \
+  })
+
+/* Remap a filename.
+
+   Returns OLD_NAME unchanged if there was no remapping, otherwise returns a
+   stack-allocated pointer to the newly-remapped filename.  */
+#define prefix_map_remap_alloca(map_head, old_name) \
+  prefix_map_remap_alloc_ (map_head, old_name, alloca)
+
+
+/* Parse prefix-maps according to the BUILD_PATH_PREFIX_MAP standard.
+
+   The input string value is of the form
+
+     dst[0]=src[0]:dst[1]=src[1]...
+
+   Every dst[i] and src[i] has had "%", "=" and ":" characters replaced with
+   "%#", "%+", and "%." respectively; this function reverses this replacement.
+
+   Rightmost entries are stored at the head of the parsed structure.
+
+   Returns 0 on failure and 1 on success.  */
+int
+prefix_map_parse (struct prefix_map **map_head, const char *arg);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _PREFIX_MAP_H */
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index bf59d0162..082770d04 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -541,6 +541,9 @@ struct cpp_callbacks
 
   /* Callback that can change a user builtin into normal macro.  */
   bool (*user_builtin_macro) (cpp_reader *, cpp_hashnode *);
+
+  /* Callback to parse BUILD_PATH_PREFIX_MAP from environment.  */
+  struct prefix_map **(*get_build_path_prefix_map) (cpp_reader *);
 };
 
 #ifdef VMS
diff --git a/libcpp/init.c b/libcpp/init.c
index 5fa82ca9c..270d42b95 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -231,6 +231,9 @@ cpp_create_reader (enum c_lang lang, hash_table *table,
   /* Do not force token locations by default.  */
   pfile->forced_token_location_p = NULL;
 
+  /* Initialize build_path_prefix_map to NULL (not yet set).  */
+  pfile->build_path_prefix_map = NULL;
+
   /* The expression parser stack.  */
   _cpp_expand_op_stack (pfile);
 
diff --git a/libcpp/internal.h b/libcpp/internal.h
index 5b3731bba..5b09bf1a4 100644
--- a/libcpp/internal.h
+++ b/libcpp/internal.h
@@ -485,6 +485,11 @@ struct cpp_reader
   const unsigned char *date;
   const unsigned char *time;
 
+  /* Externally set prefix-map to transform absolute paths, useful for
+     reproducibility.  It should be initialized to NULL (not yet set or
+     disabled) or to a `struct prefix_map` double pointer to enable it.  */
+  struct prefix_map **build_path_prefix_map;
+
   /* EOF token, and a token forcing paste avoidance.  */
   cpp_token avoid_paste;
   cpp_token eof;
diff --git a/libcpp/macro.c b/libcpp/macro.c
index 54de3e3fc..6cdd1e5d3 100644
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -28,6 +28,7 @@ along with this program; see the file COPYING3.  If not see
 #include "system.h"
 #include "cpplib.h"
 #include "internal.h"
+#include "prefix-map.h"
 
 typedef struct macro_arg macro_arg;
 /* This structure represents the tokens of a macro argument.  These
@@ -271,7 +272,17 @@ _cpp_builtin_macro_text (cpp_reader *pfile, cpp_hashnode *node)
 	unsigned int len;
 	const char *name;
 	uchar *buf;
+	struct prefix_map **map = pfile->build_path_prefix_map;
 	
+	/* Set a prefix-map for __FILE__ if BUILD_PATH_PREFIX_MAP is defined.  */
+	if (map == NULL && pfile->cb.get_build_path_prefix_map != NULL)
+	  {
+	    map = pfile->cb.get_build_path_prefix_map (pfile);
+	    if (map == NULL)
+	      abort ();
+	    pfile->build_path_prefix_map = map;
+	  }
+
 	if (node->value.builtin == BT_FILE)
 	  name = linemap_get_expansion_filename (pfile->line_table,
 						 pfile->line_table->highest_line);
@@ -281,6 +292,11 @@ _cpp_builtin_macro_text (cpp_reader *pfile, cpp_hashnode *node)
 	    if (!name)
 	      abort ();
 	  }
+
+	/* Apply the prefix-map for deterministic path output.  */
+	if (map != NULL)
+	  name = prefix_map_remap_alloca (*map, name);
+
 	len = strlen (name);
 	buf = _cpp_unaligned_alloc (pfile, len * 2 + 3);
 	result = buf;
diff --git a/libiberty/Makefile.in b/libiberty/Makefile.in
index 5280bc158..bc098496a 100644
--- a/libiberty/Makefile.in
+++ b/libiberty/Makefile.in
@@ -143,6 +143,7 @@ CFILES = alloca.c argv.c asprintf.c atexit.c				\
 	 pex-common.c pex-djgpp.c pex-msdos.c pex-one.c			\
 	 pex-unix.c pex-win32.c						\
          physmem.c putenv.c						\
+	prefix-map.c 							\
 	random.c regex.c rename.c rindex.c				\
 	safe-ctype.c setenv.c setproctitle.c sha1.c sigsetmask.c        \
 	 simple-object.c simple-object-coff.c simple-object-elf.c	\
@@ -179,6 +180,7 @@ REQUIRED_OFILES =							\
 	./partition.$(objext) ./pexecute.$(objext) ./physmem.$(objext)	\
 	./pex-common.$(objext) ./pex-one.$(objext)			\
 	./@pexecute@.$(objext)						\
+	./prefix-map.$(objext)						\
 	./safe-ctype.$(objext)						\
 	./simple-object.$(objext) ./simple-object-coff.$(objext)	\
 	./simple-object-elf.$(objext) ./simple-object-mach-o.$(objext)	\
@@ -887,7 +889,8 @@ $(CONFIGURED_OFILES): stamp-picdir
 	$(COMPILE.c) $(srcdir)/pex-one.c $(OUTPUT_OPTION)
 
 ./pex-unix.$(objext): $(srcdir)/pex-unix.c config.h $(INCDIR)/ansidecl.h \
-	$(INCDIR)/libiberty.h $(srcdir)/pex-common.h
+	$(INCDIR)/libiberty.h \
+	$(srcdir)/pex-common.h
 	if [ x"$(PICFLAG)" != x ]; then \
 	  $(COMPILE.c) $(PICFLAG) $(srcdir)/pex-unix.c -o pic/$@; \
 	else true; fi
@@ -914,6 +917,15 @@ $(CONFIGURED_OFILES): stamp-picdir
 	else true; fi
 	$(COMPILE.c) $(srcdir)/physmem.c $(OUTPUT_OPTION)
 
+./prefix-map.$(objext): $(srcdir)/prefix-map.c config.h $(INCDIR)/prefix-map.h
+	if [ x"$(PICFLAG)" != x ]; then \
+	  $(COMPILE.c) $(PICFLAG) $(srcdir)/prefix-map.c -o pic/$@; \
+	else true; fi
+	if [ x"$(NOASANFLAG)" != x ]; then \
+	  $(COMPILE.c) $(PICFLAG) $(NOASANFLAG) $(srcdir)/prefix-map.c -o noasan/$@; \
+	else true; fi
+	$(COMPILE.c) $(srcdir)/prefix-map.c $(OUTPUT_OPTION)
+
 ./putenv.$(objext): $(srcdir)/putenv.c config.h $(INCDIR)/ansidecl.h
 	if [ x"$(PICFLAG)" != x ]; then \
 	  $(COMPILE.c) $(PICFLAG) $(srcdir)/putenv.c -o pic/$@; \
diff --git a/libiberty/prefix-map.c b/libiberty/prefix-map.c
new file mode 100644
index 000000000..ecb408856
--- /dev/null
+++ b/libiberty/prefix-map.c
@@ -0,0 +1,226 @@
+/* Definitions for manipulating filename prefixes.
+
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+   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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
+
+#include "filenames.h"
+#include "libiberty.h"
+#include "prefix-map.h"
+
+
+/* Add a new mapping.
+
+   The input strings are duplicated and a new prefix_map struct is allocated.
+   Ownership of the duplicates, as well as the new prefix_map, is the same as
+   the ownership of the old struct.
+
+   Returns 0 on failure and 1 on success.  */
+int
+prefix_map_push (struct prefix_map **map_head,
+		 const char *new_prefix, const char *old_prefix)
+{
+  struct prefix_map *map = XNEW (struct prefix_map);
+  if (!map)
+    goto rewind_0;
+
+  map->old_prefix = xstrdup (old_prefix);
+  if (!map->old_prefix)
+    goto rewind_1;
+  map->old_len = strlen (old_prefix);
+
+  map->new_prefix = xstrdup (new_prefix);
+  if (!map->new_prefix)
+    goto rewind_2;
+  map->new_len = strlen (new_prefix);
+
+  map->next = *map_head;
+  *map_head = map;
+  return 1;
+
+rewind_2:
+  free ((void *) map->old_prefix);
+rewind_1:
+  free (map);
+rewind_0:
+  return 0;
+}
+
+/* Rewind a prefix map.
+
+   Everything up to the given OLD_HEAD is freed.  */
+void
+prefix_map_pop_until (struct prefix_map **map_head, struct prefix_map *old_head)
+{
+  struct prefix_map *map;
+  struct prefix_map *next;
+
+  for (map = *map_head; map != old_head; map = next)
+    {
+      free ((void *) map->old_prefix);
+      free ((void *) map->new_prefix);
+      next = map->next;
+      free (map);
+    }
+
+  *map_head = map;
+}
+
+
+/* Find a mapping suitable for the given OLD_NAME in the linked list MAP.\
+
+   If a mapping is found, writes a pointer to the non-matching suffix part of
+   OLD_NAME in SUFFIX, and its length in SUF_LEN.
+
+   Returns NULL if there was no suitable mapping.  */
+struct prefix_map *
+prefix_map_find (struct prefix_map *map, const char *old_name,
+		 const char **suffix, size_t *suf_len)
+{
+  size_t len;
+
+  for (; map; map = map->next)
+    {
+      len = map->old_len;
+      /* Ignore trailing path separators at the end of old_prefix */
+      while (len > 0 && IS_DIR_SEPARATOR (map->old_prefix[len-1])) len--;
+      /* Check if old_name matches old_prefix at a path component boundary */
+      if (! filename_ncmp (old_name, map->old_prefix, len)
+	  && (IS_DIR_SEPARATOR (old_name[len])
+	      || old_name[len] == '\0'))
+	{
+	  *suf_len = strlen (*suffix = old_name + len);
+	  break;
+	}
+    }
+
+  return map;
+}
+
+/* Prepend a prefix map before a given SUFFIX.
+
+   The remapped name is written to NEW_NAME and returned as a const pointer. No
+   allocations are performed; the caller must ensure it can hold at least
+   MAP->NEW_LEN + SUF_LEN + 1 characters.  */
+const char *
+prefix_map_prepend (struct prefix_map *map, char *new_name,
+		    const char *suffix, size_t suf_len)
+{
+  memcpy (new_name, map->new_prefix, map->new_len);
+  memcpy (new_name + map->new_len, suffix, suf_len + 1);
+  return new_name;
+}
+
+
+/* Parse a single part of a single prefix-map pair.
+
+   Returns 0 on failure and 1 on success.  */
+int
+prefix_map_parse_unquote (char *src)
+{
+  char *dest;
+  for (dest = src; 0 != (*dest = *src); ++dest, ++src)
+    switch (*src)
+      {
+      case ':':
+      case '=':
+	return 0; // should have been escaped
+      case '%':
+	switch (*(src + 1))
+	  {
+	  case '.':
+	    *dest = ':';
+	    goto unquoted;
+	  case '+':
+	    *dest = '=';
+	  unquoted:
+	  case '#':
+	    ++src;
+	    break;
+	  default:
+	    return 0; // invalid
+	  }
+      }
+  return 1;
+}
+
+/* Parse a single prefix-map.
+
+   Returns 0 on failure and 1 on success.  */
+int
+prefix_map_parse1 (struct prefix_map **map_head, char *arg)
+{
+  char *p;
+  p = strchr (arg, '=');
+  if (!p)
+    return 0;
+  *p = '\0';
+  if (!prefix_map_parse_unquote (arg))
+    return 0;
+  p++;
+  if (!prefix_map_parse_unquote (p))
+    return 0;
+
+  return prefix_map_push (map_head, arg, p);
+}
+
+/* Parse a prefix-map according to the BUILD_PATH_PREFIX_MAP standard.
+
+   The input string value is of the form
+
+     dst[0]=src[0]:dst[1]=src[1]...
+
+   Every dst[i] and src[i] has had "%", "=" and ":" characters replaced with
+   "%#", "%+", and "%." respectively; this function reverses this replacement.
+
+   Rightmost entries are stored at the head of the parsed structure.
+
+   Returns 0 on failure and 1 on success.  */
+int
+prefix_map_parse (struct prefix_map **map_head, const char *arg)
+{
+  struct prefix_map *old_head = *map_head;
+
+  size_t len = strlen (arg);
+  char *copy = (char *) alloca (len + 1);
+  memcpy (copy, arg, len + 1);
+
+  const char *sep = ":";
+  char *end, *tok = strtok_r (copy, sep, &end);
+  while (tok != NULL)
+    {
+      if (!prefix_map_parse1 (map_head, tok))
+	{
+	  prefix_map_pop_until (map_head, old_head);
+	  return 0;
+	}
+
+      tok = strtok_r (NULL, sep, &end);
+    }
+
+  return 1;
+}
-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
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