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 #ifndef TARGET_AIX
  49 #define TARGET_AIX 0
  50 #endif
  51
  52 /* This file holds all the cases where the Go frontend needs
  53    information from gcc's backend.  */
  54
  55 /* Return whether or not GCC has reported any errors.  */
  56
  57 bool
  58 saw_errors (void)
  59 {
  60   return errorcount != 0 || sorrycount != 0;
  61 }
  62
  63 /* Return the alignment in bytes of a struct field of type T.  */
  64
  65 unsigned int
  66 go_field_alignment (tree t)
  67 {
  68   unsigned int v;
  69
  70   v = TYPE_ALIGN (t);
  71
  72 #ifdef BIGGEST_FIELD_ALIGNMENT
  73   if (v > BIGGEST_FIELD_ALIGNMENT)
  74     v = BIGGEST_FIELD_ALIGNMENT;
  75 #endif
  76
  77 #ifdef ADJUST_FIELD_ALIGN
  78   v = ADJUST_FIELD_ALIGN (NULL_TREE, t, v);
  79 #endif
  80
  81   return v / BITS_PER_UNIT;
  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,
 109                          TARGET_AIX ? SECTION_EXCLUDE : SECTION_DEBUG,
 110                          NULL);
 111     }
 112
 113   switch_to_section (sec);
 114   assemble_string (bytes, size);
 115 }
 116
 117 /* The go_read_export_data function is called by the Go frontend
 118    proper to read Go export data from an object file.  FD is a file
 119    descriptor open for reading.  OFFSET is the offset within the file
 120    where the object file starts; this will be 0 except when reading an
 121    archive.  On success this returns NULL and sets *PBUF to a buffer
 122    allocated using malloc, of size *PLEN, holding the export data.  If
 123    the data is not found, this returns NULL and sets *PBUF to NULL and
 124    *PLEN to 0.  If some error occurs, this returns an error message
 125    and sets *PERR to an errno value or 0 if there is no relevant
 126    errno.  */
 127
 128 const char *
 129 go_read_export_data (int fd, off_t offset, char **pbuf, size_t *plen,
 130                      int *perr)
 131 {
 132   simple_object_read *sobj;
 133   const char *errmsg;
 134   off_t sec_offset;
 135   off_t sec_length;
 136   int found;
 137   char *buf;
 138   ssize_t c;
 139
 140   *pbuf = NULL;
 141   *plen = 0;
 142
 143   sobj = simple_object_start_read (fd, offset, GO_EXPORT_SEGMENT_NAME,
 144                                    &errmsg, perr);
 145   if (sobj == NULL)
 146     {
 147       /* If we get an error here, just pretend that we didn't find any
 148          export data.  This is the right thing to do if the error is
 149          that the file was not recognized as an object file.  This
 150          will ignore file I/O errors, but it's not too big a deal
 151          because we will wind up giving some other error later.  */
 152       return NULL;
 153     }
 154
 155   found = simple_object_find_section (sobj, GO_EXPORT_SECTION_NAME,
 156                                       &sec_offset, &sec_length,
 157                                       &errmsg, perr);
 158   simple_object_release_read (sobj);
 159   if (!found)
 160     return errmsg;
 161
 162   if (lseek (fd, offset + sec_offset, SEEK_SET) < 0)
 163     {
 164       *perr = errno;
 165       return _("lseek failed while reading export data");
 166     }
 167
 168   buf = XNEWVEC (char, sec_length);
 169   if (buf == NULL)
 170     {
 171       *perr = errno;
 172       return _("memory allocation failed while reading export data");
 173     }
 174
 175   c = read (fd, buf, sec_length);
 176   if (c < 0)
 177     {
 178       *perr = errno;
 179       free (buf);
 180       return _("read failed while reading export data");
 181     }
 182
 183   if (c < sec_length)
 184     {
 185       free (buf);
 186       return _("short read while reading export data");
 187     }
 188
 189   *pbuf = buf;
 190   *plen = sec_length;
 191
 192   return NULL;
 193 }