emacs/src/android-emacs.c

/* Android initialization for GNU Emacs.

Copyright (C) 2023-2024 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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.

GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>
#include <stdio.h>
#include <alloca.h>
#include <string.h>
#include <unistd.h>

/* android-emacs is a wrapper around /system/bin/app_process(64).
   It invokes app_process(64) with the right class path and then
   starts org.gnu.emacs.EmacsNoninteractive.

   The main function in that class tries to load an activity thread
   and obtain a context and asset manager before calling
   android_emacs_init, which is required for Emacs to find required
   preloaded Lisp.  */

int
main (int argc, char **argv)
{
  char **args;
  int i;
  char *bootclasspath, *emacs_class_path, *ld_library_path;

  /* Allocate enough to hold the arguments to app_process.  */
  args = alloca ((10 + argc) * sizeof *args);

  /* Clear args.  */
  memset (args, 0, (10 + argc) * sizeof *args);

  /* First, figure out what program to start.  */
#if defined __x86_64__ || defined __aarch64__ || defined __mips64
  args[0] = (char *) "/system/bin/app_process64";
#else /* i386 || regular mips || arm */
  args[0] = (char *) "/system/bin/app_process";
#endif /* __x86_64__ || __aarch64__ || __mips64 */

  /* Machines with ART require the boot classpath to be manually
     specified.  Machines with Dalvik however refuse to do so, as they
     open the jars inside the BOOTCLASSPATH environment variable at
     startup, resulting in the following crash:

     W/dalvikvm( 1608): Refusing to reopen boot DEX
     '/system/framework/core.jar'
     W/dalvikvm( 1608): Refusing to reopen boot DEX
     '/system/framework/bouncycastle.jar'
     E/dalvikvm( 1608): Too many exceptions during init (failed on
     'Ljava/io/IOException;' 'Re-opening BOOTCLASSPATH DEX files is
     not allowed')
     E/dalvikvm( 1608): VM aborting  */

#if HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL
  if (android_get_device_api_level () < 21)
    {
      bootclasspath = NULL;
      goto skip_setup;
    }
#else /* !HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL */
  if (__ANDROID_API__ < 21)
    {
      bootclasspath = NULL;
      goto skip_setup;
    }
#endif /* HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL */

  /* Next, obtain the boot class path.  */
  bootclasspath = getenv ("BOOTCLASSPATH");

  if (!bootclasspath)
    {
      fprintf (stderr, "The BOOTCLASSPATH environment variable"
	       " is not set.  As a result, Emacs does not know"
	       " how to start app_process.\n"
	       "This is likely a change in the Android platform."
	       "  Please report this to bug-gnu-emacs@gnu.org.\n");
      return 1;
    }

 skip_setup:

  /* And the Emacs class path.  */
  emacs_class_path = getenv ("EMACS_CLASS_PATH");

  if (!emacs_class_path)
    {
      fprintf (stderr, "EMACS_CLASS_PATH not set."
	       "  Please make sure Emacs is being started"
	       " from within a running copy of Emacs.\n");
      return 1;
    }

  /* Restore LD_LIBRARY_PATH to its original value, the app library
     directory, to guarantee that it is possible for Java to find the
     Emacs C code later.  */

  ld_library_path = getenv ("EMACS_LD_LIBRARY_PATH");

  if (ld_library_path)
    setenv ("LD_LIBRARY_PATH", ld_library_path, 1);

  if (bootclasspath)
    {
      if (asprintf (&bootclasspath, "-Djava.class.path=%s:%s",
		    bootclasspath, emacs_class_path) < 0)
	{
	  perror ("asprintf");
	  return 1;
	}
    }
  else
    {
      if (asprintf (&bootclasspath, "-Djava.class.path=%s",
		    emacs_class_path) < 0)
	{
	  perror ("asprintf");
	  return 1;
	}
    }

  args[1] = bootclasspath;
  args[2] = (char *) "/system/bin";

#if HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL
  /* I don't know exactly when --nice-name was introduced; this is
     just a guess.  */
  if (android_get_device_api_level () >= 26)
    {
      args[3] = (char *) "--nice-name=emacs";
      args[4] = (char *) "org.gnu.emacs.EmacsNoninteractive";

      /* Arguments from here on are passed to main in
	 EmacsNoninteractive.java.  */
      args[5] = argv[0];

      /* Now copy the rest of the arguments over.  */
      for (i = 1; i < argc; ++i)
	args[5 + i] = argv[i];
    }
  else
    {
#endif /* HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL */
      args[3] = (char *) "org.gnu.emacs.EmacsNoninteractive";

      /* Arguments from here on are passed to main in
	 EmacsNoninteractive.java.  */
      args[4] = argv[0];

      /* Now copy the rest of the arguments over.  */
      for (i = 1; i < argc; ++i)
	args[4 + i] = argv[i];
#if HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL
    }
#endif /* HAVE_DECL_ANDROID_GET_DEVICE_API_LEVEL */

  /* Finally, try to start the app_process.  */
  execvp (args[0], args);

  /* If exit fails, return an error indication.  */
  perror ("exec");
  return 1;
}