gcc/go/go-backend.c

   1 /* go-backend.c -- Go frontend interface to gcc backend.
   2    Copyright (C) 2010-2020 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 cannot do type-based alias
  86    analysis.  */
  87
  88 void
  89 go_imported_unsafe (void)
  90 {
  91   flag_strict_aliasing = false;
  92   TREE_OPTIMIZATION (optimization_default_node)->x_flag_strict_aliasing = false;
  93
  94   /* Let the backend know that the options have changed.  */
  95   targetm.override_options_after_change ();
  96 }
  97
  98 /* This is called by the Go frontend proper to add data to the
  99    section containing Go export data.  */
 100
 101 void
 102 go_write_export_data (const char *bytes, unsigned int size)
 103 {
 104   static section* sec;
 105
 106   if (sec == NULL)
 107     {
 108       gcc_assert (targetm_common.have_named_sections);
 109       sec = get_section (GO_EXPORT_SECTION_NAME,
 110                          TARGET_AIX ? SECTION_EXCLUDE : SECTION_DEBUG,
 111                          NULL);
 112     }
 113
 114   switch_to_section (sec);
 115   assemble_string (bytes, size);
 116 }
 117
 118 /* The go_read_export_data function is called by the Go frontend
 119    proper to read Go export data from an object file.  FD is a file
 120    descriptor open for reading.  OFFSET is the offset within the file
 121    where the object file starts; this will be 0 except when reading an
 122    archive.  On success this returns NULL and sets *PBUF to a buffer
 123    allocated using malloc, of size *PLEN, holding the export data.  If
 124    the data is not found, this returns NULL and sets *PBUF to NULL and
 125    *PLEN to 0.  If some error occurs, this returns an error message
 126    and sets *PERR to an errno value or 0 if there is no relevant
 127    errno.  */
 128
 129 const char *
 130 go_read_export_data (int fd, off_t offset, char **pbuf, size_t *plen,
 131                      int *perr)
 132 {
 133   simple_object_read *sobj;
 134   const char *errmsg;
 135   off_t sec_offset;
 136   off_t sec_length;
 137   int found;
 138   char *buf;
 139   ssize_t c;
 140
 141   *pbuf = NULL;
 142   *plen = 0;
 143
 144   sobj = simple_object_start_read (fd, offset, GO_EXPORT_SEGMENT_NAME,
 145                                    &errmsg, perr);
 146   if (sobj == NULL)
 147     {
 148       /* If we get an error here, just pretend that we didn't find any
 149          export data.  This is the right thing to do if the error is
 150          that the file was not recognized as an object file.  This
 151          will ignore file I/O errors, but it's not too big a deal
 152          because we will wind up giving some other error later.  */
 153       return NULL;
 154     }
 155
 156   found = simple_object_find_section (sobj, GO_EXPORT_SECTION_NAME,
 157                                       &sec_offset, &sec_length,
 158                                       &errmsg, perr);
 159   simple_object_release_read (sobj);
 160   if (!found)
 161     return errmsg;
 162
 163   if (lseek (fd, offset + sec_offset, SEEK_SET) < 0)
 164     {
 165       *perr = errno;
 166       return _("lseek failed while reading export data");
 167     }
 168
 169   buf = XNEWVEC (char, sec_length);
 170   if (buf == NULL)
 171     {
 172       *perr = errno;
 173       return _("memory allocation failed while reading export data");
 174     }
 175
 176   c = read (fd, buf, sec_length);
 177   if (c < 0)
 178     {
 179       *perr = errno;
 180       free (buf);
 181       return _("read failed while reading export data");
 182     }
 183
 184   if (c < sec_length)
 185     {
 186       free (buf);
 187       return _("short read while reading export data");
 188     }
 189
 190   *pbuf = buf;
 191   *plen = sec_length;
 192
 193   return NULL;
 194 }