gcc/go/go-backend.c

   1 /* go-backend.c -- Go frontend interface to gcc backend.
   2    Copyright (C) 2010-2017 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 "memmodel.h"
  26 #include "tm_p.h"
  27 #include "diagnostic.h"
  28 #include "simple-object.h"
  29 #include "stor-layout.h"
  30 #include "intl.h"
  31 #include "output.h"     /* for assemble_string */
  32 #include "common/common-target.h"
  33 #include "go-c.h"
  34
  35 /* The segment name we pass to simple_object_start_read to find Go
  36    export data.  */
  37
  38 #ifndef GO_EXPORT_SEGMENT_NAME
  39 #define GO_EXPORT_SEGMENT_NAME "__GNU_GO"
  40 #endif
  41
  42 /* The section name we use when reading and writing export data.  */
  43
  44 #ifndef GO_EXPORT_SECTION_NAME
  45 #define GO_EXPORT_SECTION_NAME ".go_export"
  46 #endif
  47
  48 /* This file holds all the cases where the Go frontend needs
  49    information from gcc's backend.  */
  50
  51 /* Return whether or not GCC has reported any errors.  */
  52
  53 bool
  54 saw_errors (void)
  55 {
  56   return errorcount != 0 || sorrycount != 0;
  57 }
  58
  59 /* Return the alignment in bytes of a struct field of type T.  */
  60
  61 unsigned int
  62 go_field_alignment (tree t)
  63 {
  64   unsigned int v;
  65
  66   v = TYPE_ALIGN (t);
  67
  68 #ifdef BIGGEST_FIELD_ALIGNMENT
  69   if (v > BIGGEST_FIELD_ALIGNMENT)
  70     v = BIGGEST_FIELD_ALIGNMENT;
  71 #endif
  72
  73 #ifdef ADJUST_FIELD_ALIGN
  74   v = ADJUST_FIELD_ALIGN (NULL_TREE, t, v);
  75 #endif
  76
  77   return v / BITS_PER_UNIT;
  78 }
  79
  80 /* This is called by the Go frontend proper if the unsafe package was
  81    imported.  When that happens we can not do type-based alias
  82    analysis.  */
  83
  84 void
  85 go_imported_unsafe (void)
  86 {
  87   flag_strict_aliasing = false;
  88
  89   /* Let the backend know that the options have changed.  */
  90   targetm.override_options_after_change ();
  91 }
  92
  93 /* This is called by the Go frontend proper to add data to the
  94    section containing Go export data.  */
  95
  96 void
  97 go_write_export_data (const char *bytes, unsigned int size)
  98 {
  99   static section* sec;
 100
 101   if (sec == NULL)
 102     {
 103       gcc_assert (targetm_common.have_named_sections);
 104       sec = get_section (GO_EXPORT_SECTION_NAME, SECTION_DEBUG, NULL);
 105     }
 106
 107   switch_to_section (sec);
 108   assemble_string (bytes, size);
 109 }
 110
 111 /* The go_read_export_data function is called by the Go frontend
 112    proper to read Go export data from an object file.  FD is a file
 113    descriptor open for reading.  OFFSET is the offset within the file
 114    where the object file starts; this will be 0 except when reading an
 115    archive.  On success this returns NULL and sets *PBUF to a buffer
 116    allocated using malloc, of size *PLEN, holding the export data.  If
 117    the data is not found, this returns NULL and sets *PBUF to NULL and
 118    *PLEN to 0.  If some error occurs, this returns an error message
 119    and sets *PERR to an errno value or 0 if there is no relevant
 120    errno.  */
 121
 122 const char *
 123 go_read_export_data (int fd, off_t offset, char **pbuf, size_t *plen,
 124                      int *perr)
 125 {
 126   simple_object_read *sobj;
 127   const char *errmsg;
 128   off_t sec_offset;
 129   off_t sec_length;
 130   int found;
 131   char *buf;
 132   ssize_t c;
 133
 134   *pbuf = NULL;
 135   *plen = 0;
 136
 137   sobj = simple_object_start_read (fd, offset, GO_EXPORT_SEGMENT_NAME,
 138                                    &errmsg, perr);
 139   if (sobj == NULL)
 140     {
 141       /* If we get an error here, just pretend that we didn't find any
 142          export data.  This is the right thing to do if the error is
 143          that the file was not recognized as an object file.  This
 144          will ignore file I/O errors, but it's not too big a deal
 145          because we will wind up giving some other error later.  */
 146       return NULL;
 147     }
 148
 149   found = simple_object_find_section (sobj, GO_EXPORT_SECTION_NAME,
 150                                       &sec_offset, &sec_length,
 151                                       &errmsg, perr);
 152   simple_object_release_read (sobj);
 153   if (!found)
 154     return errmsg;
 155
 156   if (lseek (fd, offset + sec_offset, SEEK_SET) < 0)
 157     {
 158       *perr = errno;
 159       return _("lseek failed while reading export data");
 160     }
 161
 162   buf = XNEWVEC (char, sec_length);
 163   if (buf == NULL)
 164     {
 165       *perr = errno;
 166       return _("memory allocation failed while reading export data");
 167     }
 168
 169   c = read (fd, buf, sec_length);
 170   if (c < 0)
 171     {
 172       *perr = errno;
 173       free (buf);
 174       return _("read failed while reading export data");
 175     }
 176
 177   if (c < sec_length)
 178     {
 179       free (buf);
 180       return _("short read while reading export data");
 181     }
 182
 183   *pbuf = buf;
 184   *plen = sec_length;
 185
 186   return NULL;
 187 }