gcc/go/go-backend.c

   1 /* go-backend.c -- Go frontend interface to gcc backend.
   2    Copyright (C) 2010-2013 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "simple-object.h"
  24 #include "tm.h"
  25 #include "tree.h"
  26 #include "tm_p.h"
  27 #include "intl.h"
  28 #include "output.h"     /* for assemble_string */
  29 #include "target.h"
  30 #include "common/common-target.h"
  31
  32 #include "go-c.h"
  33
  34 /* The segment name we pass to simple_object_start_read to find Go
  35    export data.  */
  36
  37 #ifndef GO_EXPORT_SEGMENT_NAME
  38 #define GO_EXPORT_SEGMENT_NAME "__GNU_GO"
  39 #endif
  40
  41 /* The section name we use when reading and writing export data.  */
  42
  43 #ifndef GO_EXPORT_SECTION_NAME
  44 #define GO_EXPORT_SECTION_NAME ".go_export"
  45 #endif
  46
  47 /* This file holds all the cases where the Go frontend needs
  48    information from gcc's backend.  */
  49
  50 /* Return the alignment in bytes of a struct field of type T.  */
  51
  52 unsigned int
  53 go_field_alignment (tree t)
  54 {
  55   unsigned int v;
  56
  57   v = TYPE_ALIGN (t);
  58
  59 #ifdef BIGGEST_FIELD_ALIGNMENT
  60   if (v > BIGGEST_FIELD_ALIGNMENT)
  61     v = BIGGEST_FIELD_ALIGNMENT;
  62 #endif
  63
  64 #ifdef ADJUST_FIELD_ALIGN
  65   {
  66     tree field ATTRIBUTE_UNUSED;
  67     field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL, t);
  68     v = ADJUST_FIELD_ALIGN (field, v);
  69   }
  70 #endif
  71
  72   return v / BITS_PER_UNIT;
  73 }
  74
  75 /* Return the size and alignment of a trampoline.  */
  76
  77 void
  78 go_trampoline_info (unsigned int *size, unsigned int *alignment)
  79 {
  80   *size = TRAMPOLINE_SIZE;
  81   *alignment = TRAMPOLINE_ALIGNMENT;
  82 }
  83
  84 /* This is called by the Go frontend proper if the unsafe package was
  85    imported.  When that happens we can not do type-based alias
  86    analysis.  */
  87
  88 void
  89 go_imported_unsafe (void)
  90 {
  91   flag_strict_aliasing = false;
  92
  93   /* Let the backend know that the options have changed.  */
  94   targetm.override_options_after_change ();
  95 }
  96
  97 /* This is called by the Go frontend proper to add data to the
  98    section containing Go export data.  */
  99
 100 void
 101 go_write_export_data (const char *bytes, unsigned int size)
 102 {
 103   static section* sec;
 104
 105   if (sec == NULL)
 106     {
 107       gcc_assert (targetm_common.have_named_sections);
 108       sec = get_section (GO_EXPORT_SECTION_NAME, SECTION_DEBUG, NULL);
 109     }
 110
 111   switch_to_section (sec);
 112   assemble_string (bytes, size);
 113 }
 114
 115 /* The go_read_export_data function is called by the Go frontend
 116    proper to read Go export data from an object file.  FD is a file
 117    descriptor open for reading.  OFFSET is the offset within the file
 118    where the object file starts; this will be 0 except when reading an
 119    archive.  On success this returns NULL and sets *PBUF to a buffer
 120    allocated using malloc, of size *PLEN, holding the export data.  If
 121    the data is not found, this returns NULL and sets *PBUF to NULL and
 122    *PLEN to 0.  If some error occurs, this returns an error message
 123    and sets *PERR to an errno value or 0 if there is no relevant
 124    errno.  */
 125
 126 const char *
 127 go_read_export_data (int fd, off_t offset, char **pbuf, size_t *plen,
 128                      int *perr)
 129 {
 130   simple_object_read *sobj;
 131   const char *errmsg;
 132   off_t sec_offset;
 133   off_t sec_length;
 134   int found;
 135   char *buf;
 136   ssize_t c;
 137
 138   *pbuf = NULL;
 139   *plen = 0;
 140
 141   sobj = simple_object_start_read (fd, offset, GO_EXPORT_SEGMENT_NAME,
 142                                    &errmsg, perr);
 143   if (sobj == NULL)
 144     {
 145       /* If we get an error here, just pretend that we didn't find any
 146          export data.  This is the right thing to do if the error is
 147          that the file was not recognized as an object file.  This
 148          will ignore file I/O errors, but it's not too big a deal
 149          because we will wind up giving some other error later.  */
 150       return NULL;
 151     }
 152
 153   found = simple_object_find_section (sobj, GO_EXPORT_SECTION_NAME,
 154                                       &sec_offset, &sec_length,
 155                                       &errmsg, perr);
 156   simple_object_release_read (sobj);
 157   if (!found)
 158     return errmsg;
 159
 160   if (lseek (fd, offset + sec_offset, SEEK_SET) < 0)
 161     {
 162       *perr = errno;
 163       return _("lseek failed while reading export data");
 164     }
 165
 166   buf = XNEWVEC (char, sec_length);
 167   if (buf == NULL)
 168     {
 169       *perr = errno;
 170       return _("memory allocation failed while reading export data");
 171     }
 172
 173   c = read (fd, buf, sec_length);
 174   if (c < 0)
 175     {
 176       *perr = errno;
 177       free (buf);
 178       return _("read failed while reading export data");
 179     }
 180
 181   if (c < sec_length)
 182     {
 183       free (buf);
 184       return _("short read while reading export data");
 185     }
 186
 187   *pbuf = buf;
 188   *plen = sec_length;
 189
 190   return NULL;
 191 }