bison: add command line option to map file prefixes

Teaches bison about a new command line option, --file-prefix-map OLD=NEW
(based on the -ffile-prefix-map option from GCC) which causes it to
replace and file path of OLD in the text of the output file with NEW,
mainly for header guards and comments. The primary use of this is to
make builds reproducible with different input paths, and in particular
the debugging information produced when the source code is compiled. For
example, a distro may know that the bison source code will be located at
"/usr/src/bison" and thus can generate bison files that are reproducible
with the following command:

    bison --output=/build/bison/parse.c -d --file-prefix-map=/build/bison/=/usr/src/bison/ parse.y

Importantly, this will change the header guards and #line directives
from:

    #ifndef YY_BUILD_BISON_PARSE_H
    #line 100 "/build/bison/parse.h"

to

    #ifndef YY_USR_SRC_BISON_PARSE_H
    #line 100 "/usr/src/bison/parse.h"

which is reproducible.

See https://lists.gnu.org/r/bison-patches/2020-05/msg00016.html
Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>

* src/files.h, src/files.c (spec_mapped_header_file)
(mapped_dir_prefix, map_file_name, add_prefix_map): New.
* src/getargs.c (-M, --file-prefix-map): New option.
* src/output.c (prepare): Define b4_mapped_dir_prefix and
b4_spec_header_file.
* src/scan-skel.l (@ofile@): Output the mapped file name.
* data/skeletons/glr.c, data/skeletons/glr.cc,
* data/skeletons/lalr1.cc, data/skeletons/location.cc,
* data/skeletons/yacc.c:
Adjust.
* doc/bison.texi: Document.
* tests/input.at, tests/output.at: Check.

src/files.c

@@ -25,6 +25,8 @@
 #include <dirname.h>
 #include <error.h>
 #include <get-errno.h>
+#include <gl_array_list.h>
+#include <gl_xlist.h>
 #include <quote.h>
 #include <quotearg.h>
 #include <relocatable.h> /* relocate2 */
@@ -55,6 +57,7 @@ char *spec_verbose_file = NULL;  /* for --verbose. */
 char *spec_graph_file = NULL;    /* for -g. */
 char *spec_xml_file = NULL;      /* for -x. */
 char *spec_header_file = NULL;  /* for --defines. */
+char *spec_mapped_header_file = NULL;
 char *parser_file_name;
 
 /* All computed output file names.  */
@@ -91,11 +94,20 @@ uniqstr grammar_file = NULL;
 char *all_but_ext;
 static char *all_but_tab_ext;
 char *dir_prefix;
+char *mapped_dir_prefix;
 
 /* C source file extension (the parser source).  */
 static char *src_extension = NULL;
 /* Header file extension (if option '`-d'' is specified).  */
 static char *header_extension = NULL;
+
+struct prefix_map
+{
+  char *oldprefix;
+  char *newprefix;
+};
+
+static gl_list_t prefix_maps = NULL;
 
 /*-----------------------------------------------------------------.
 | Return a newly allocated string composed of the concatenation of |
@@ -159,6 +171,70 @@ xfdopen (int fd, char const *mode)
   return res;
 }
 
+/*  Given an input file path, returns a dynamically allocated string that
+    contains the path with the file prefix mapping rules applied, or NULL if
+    the input was NULL. */
+char *
+map_file_name (char const *filename)
+{
+  if (!filename)
+    return NULL;
+
+  struct prefix_map const *p = NULL;
+  if (prefix_maps)
+    {
+      void const *ptr;
+      gl_list_iterator_t iter = gl_list_iterator (prefix_maps);
+      while (gl_list_iterator_next (&iter, &ptr, NULL))
+        {
+          p = ptr;
+          if (strncmp (p->oldprefix, filename, strlen (p->oldprefix)) == 0)
+            break;
+          p = NULL;
+        }
+      gl_list_iterator_free (&iter);
+    }
+
+  if (!p)
+    return xstrdup (filename);
+
+  size_t oldprefix_len = strlen (p->oldprefix);
+  size_t newprefix_len = strlen (p->newprefix);
+  char *s = xmalloc (newprefix_len + strlen (filename) - oldprefix_len + 1);
+
+  char *end = stpcpy (s, p->newprefix);
+  stpcpy (end, filename + oldprefix_len);
+
+  return s;
+}
+
+static void
+prefix_map_free (struct prefix_map *p)
+{
+  free (p->oldprefix);
+  free (p->newprefix);
+  free (p);
+}
+
+/*  Adds a new file prefix mapping. If a file path starts with oldprefix, it
+    will be replaced with newprefix */
+void
+add_prefix_map(char const* oldprefix, char const* newprefix)
+{
+  if (!prefix_maps)
+    prefix_maps = gl_list_create_empty (GL_ARRAY_LIST,
+                                        /* equals */ NULL,
+                                        /* hashcode */ NULL,
+                                        (gl_listelement_dispose_fn) prefix_map_free,
+                                        true);
+
+  struct prefix_map *p = xmalloc (sizeof (*p));
+  p->oldprefix = xstrdup (oldprefix);
+  p->newprefix = xstrdup (newprefix);
+
+  gl_list_add_last (prefix_maps, p);
+}
+
 /*------------------------------------------------------------------.
 | Compute ALL_BUT_EXT, ALL_BUT_TAB_EXT and output files extensions. |
 `------------------------------------------------------------------*/
@@ -363,6 +439,9 @@ compute_output_file_names (void)
       output_file_name_check (&spec_verbose_file, false);
     }
 
+  spec_mapped_header_file = map_file_name (spec_header_file);
+  mapped_dir_prefix = map_file_name (dir_prefix);
+
   free (all_but_tab_ext);
   free (src_extension);
   free (header_extension);
@@ -449,10 +528,15 @@ output_file_names_free (void)
   free (spec_graph_file);
   free (spec_xml_file);
   free (spec_header_file);
+  free (spec_mapped_header_file);
   free (parser_file_name);
   free (dir_prefix);
+  free (mapped_dir_prefix);
   for (int i = 0; i < generated_files_size; i++)
     free (generated_files[i].name);
   free (generated_files);
   free (relocate_buffer);
+
+  if (prefix_maps)
+    gl_list_free (prefix_maps);
 }