gcc/go/go-backend.c

   1 /* go-backend.c -- Go frontend interface to gcc backend.
   2    Copyright (C) 2010-2016 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 "target.h"
  24 #include "tree.h"
  25 #include "tm_p.h"
  26 #include "diagnostic.h"
  27 #include "simple-object.h"
  28 #include "stor-layout.h"
  29 #include "intl.h"
  30 #include "output.h"     /* for assemble_string */
  31 #include "common/common-target.h"
  32
  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 whether or not GCC has reported any errors.  */
  51
  52 bool
  53 saw_errors (void)
  54 {
  55   return errorcount != 0 || sorrycount != 0;
  56 }
  57
  58 /* Return the alignment in bytes of a struct field of type T.  */
  59
  60 unsigned int
  61 go_field_alignment (tree t)
  62 {
  63   unsigned int v;
  64
  65   v = TYPE_ALIGN (t);
  66
  67 #ifdef BIGGEST_FIELD_ALIGNMENT
  68   if (v > BIGGEST_FIELD_ALIGNMENT)
  69     v = BIGGEST_FIELD_ALIGNMENT;
  70 #endif
  71
  72 #ifdef ADJUST_FIELD_ALIGN
  73   {
  74     tree field ATTRIBUTE_UNUSED;
  75     field = build_decl (UNKNOWN_LOCATION, FIELD_DECL, NULL, t);
  76     v = ADJUST_FIELD_ALIGN (field, v);
  77   }
  78 #endif
  79
  80   return v / BITS_PER_UNIT;
  81 }
  82
  83 /* Return the size and alignment of a trampoline.  */
  84
  85 void
  86 go_trampoline_info (unsigned int *size, unsigned int *alignment)
  87 {
  88   *size = TRAMPOLINE_SIZE;
  89   *alignment = TRAMPOLINE_ALIGNMENT;
  90 }
  91
  92 /* This is called by the Go frontend proper if the unsafe package was
  93    imported.  When that happens we can not do type-based alias
  94    analysis.  */
  95
  96 void
  97 go_imported_unsafe (void)
  98 {
  99   flag_strict_aliasing = false;
 100
 101   /* Let the backend know that the options have changed.  */
 102   targetm.override_options_after_change ();
 103 }
 104
 105 /* This is called by the Go frontend proper to add data to the
 106    section containing Go export data.  */
 107
 108 void
 109 go_write_export_data (const char *bytes, unsigned int size)
 110 {
 111   static section* sec;
 112
 113   if (sec == NULL)
 114     {
 115       gcc_assert (targetm_common.have_named_sections);
 116       sec = get_section (GO_EXPORT_SECTION_NAME, SECTION_DEBUG, NULL);
 117     }
 118
 119   switch_to_section (sec);
 120   assemble_string (bytes, size);
 121 }
 122
 123 /* The go_read_export_data function is called by the Go frontend
 124    proper to read Go export data from an object file.  FD is a file
 125    descriptor open for reading.  OFFSET is the offset within the file
 126    where the object file starts; this will be 0 except when reading an
 127    archive.  On success this returns NULL and sets *PBUF to a buffer
 128    allocated using malloc, of size *PLEN, holding the export data.  If
 129    the data is not found, this returns NULL and sets *PBUF to NULL and
 130    *PLEN to 0.  If some error occurs, this returns an error message
 131    and sets *PERR to an errno value or 0 if there is no relevant
 132    errno.  */
 133
 134 const char *
 135 go_read_export_data (int fd, off_t offset, char **pbuf, size_t *plen,
 136                      int *perr)
 137 {
 138   simple_object_read *sobj;
 139   const char *errmsg;
 140   off_t sec_offset;
 141   off_t sec_length;
 142   int found;
 143   char *buf;
 144   ssize_t c;
 145
 146   *pbuf = NULL;
 147   *plen = 0;
 148
 149   sobj = simple_object_start_read (fd, offset, GO_EXPORT_SEGMENT_NAME,
 150                                    &errmsg, perr);
 151   if (sobj == NULL)
 152     {
 153       /* If we get an error here, just pretend that we didn't find any
 154          export data.  This is the right thing to do if the error is
 155          that the file was not recognized as an object file.  This
 156          will ignore file I/O errors, but it's not too big a deal
 157          because we will wind up giving some other error later.  */
 158       return NULL;
 159     }
 160
 161   found = simple_object_find_section (sobj, GO_EXPORT_SECTION_NAME,
 162                                       &sec_offset, &sec_length,
 163                                       &errmsg, perr);
 164   simple_object_release_read (sobj);
 165   if (!found)
 166     return errmsg;
 167
 168   if (lseek (fd, offset + sec_offset, SEEK_SET) < 0)
 169     {
 170       *perr = errno;
 171       return _("lseek failed while reading export data");
 172     }
 173
 174   buf = XNEWVEC (char, sec_length);
 175   if (buf == NULL)
 176     {
 177       *perr = errno;
 178       return _("memory allocation failed while reading export data");
 179     }
 180
 181   c = read (fd, buf, sec_length);
 182   if (c < 0)
 183     {
 184       *perr = errno;
 185       free (buf);
 186       return _("read failed while reading export data");
 187     }
 188
 189   if (c < sec_length)
 190     {
 191       free (buf);
 192       return _("short read while reading export data");
 193     }
 194
 195   *pbuf = buf;
 196   *plen = sec_length;
 197
 198   return NULL;
 199 }