libctf/ctf-decl.c

   1 /* C declarator syntax glue.
   2    Copyright (C) 2019-2020 Free Software Foundation, Inc.
   3
   4    This file is part of libctf.
   5
   6    libctf 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    This program is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  14    See the GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; see the file COPYING.  If not see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 /* CTF Declaration Stack
  21
  22    In order to implement ctf_type_name(), we must convert a type graph back
  23    into a C type declaration.  Unfortunately, a type graph represents a storage
  24    class ordering of the type whereas a type declaration must obey the C rules
  25    for operator precedence, and the two orderings are frequently in conflict.
  26    For example, consider these CTF type graphs and their C declarations:
  27
  28    CTF_K_POINTER -> CTF_K_FUNCTION -> CTF_K_INTEGER  : int (*)()
  29    CTF_K_POINTER -> CTF_K_ARRAY -> CTF_K_INTEGER     : int (*)[]
  30
  31    In each case, parentheses are used to raise operator * to higher lexical
  32    precedence, so the string form of the C declaration cannot be constructed by
  33    walking the type graph links and forming the string from left to right.
  34
  35    The functions in this file build a set of stacks from the type graph nodes
  36    corresponding to the C operator precedence levels in the appropriate order.
  37    The code in ctf_type_name() can then iterate over the levels and nodes in
  38    lexical precedence order and construct the final C declaration string.  */
  39
  40 #include <ctf-impl.h>
  41 #include <string.h>
  42
  43 void
  44 ctf_decl_init (ctf_decl_t *cd)
  45 {
  46   int i;
  47
  48   memset (cd, 0, sizeof (ctf_decl_t));
  49
  50   for (i = CTF_PREC_BASE; i < CTF_PREC_MAX; i++)
  51     cd->cd_order[i] = CTF_PREC_BASE - 1;
  52
  53   cd->cd_qualp = CTF_PREC_BASE;
  54   cd->cd_ordp = CTF_PREC_BASE;
  55 }
  56
  57 void
  58 ctf_decl_fini (ctf_decl_t *cd)
  59 {
  60   ctf_decl_node_t *cdp, *ndp;
  61   int i;
  62
  63   for (i = CTF_PREC_BASE; i < CTF_PREC_MAX; i++)
  64     {
  65       for (cdp = ctf_list_next (&cd->cd_nodes[i]); cdp != NULL; cdp = ndp)
  66         {
  67           ndp = ctf_list_next (cdp);
  68           free (cdp);
  69         }
  70     }
  71 }
  72
  73 void
  74 ctf_decl_push (ctf_decl_t *cd, ctf_file_t *fp, ctf_id_t type)
  75 {
  76   ctf_decl_node_t *cdp;
  77   ctf_decl_prec_t prec;
  78   uint32_t kind, n = 1;
  79   int is_qual = 0;
  80
  81   const ctf_type_t *tp;
  82   ctf_arinfo_t ar;
  83
  84   if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
  85     {
  86       cd->cd_err = fp->ctf_errno;
  87       return;
  88     }
  89
  90   switch (kind = LCTF_INFO_KIND (fp, tp->ctt_info))
  91     {
  92     case CTF_K_ARRAY:
  93       (void) ctf_array_info (fp, type, &ar);
  94       ctf_decl_push (cd, fp, ar.ctr_contents);
  95       n = ar.ctr_nelems;
  96       prec = CTF_PREC_ARRAY;
  97       break;
  98
  99     case CTF_K_TYPEDEF:
 100       if (ctf_strptr (fp, tp->ctt_name)[0] == '\0')
 101         {
 102           ctf_decl_push (cd, fp, tp->ctt_type);
 103           return;
 104         }
 105       prec = CTF_PREC_BASE;
 106       break;
 107
 108     case CTF_K_FUNCTION:
 109       ctf_decl_push (cd, fp, tp->ctt_type);
 110       prec = CTF_PREC_FUNCTION;
 111       break;
 112
 113     case CTF_K_POINTER:
 114       ctf_decl_push (cd, fp, tp->ctt_type);
 115       prec = CTF_PREC_POINTER;
 116       break;
 117
 118     case CTF_K_SLICE:
 119       ctf_decl_push (cd, fp, ctf_type_reference (fp, type));
 120       prec = CTF_PREC_BASE;
 121       break;
 122
 123     case CTF_K_VOLATILE:
 124     case CTF_K_CONST:
 125     case CTF_K_RESTRICT:
 126       ctf_decl_push (cd, fp, tp->ctt_type);
 127       prec = cd->cd_qualp;
 128       is_qual++;
 129       break;
 130
 131     default:
 132       prec = CTF_PREC_BASE;
 133     }
 134
 135   if ((cdp = malloc (sizeof (ctf_decl_node_t))) == NULL)
 136     {
 137       cd->cd_err = EAGAIN;
 138       return;
 139     }
 140
 141   cdp->cd_type = type;
 142   cdp->cd_kind = kind;
 143   cdp->cd_n = n;
 144
 145   if (ctf_list_next (&cd->cd_nodes[prec]) == NULL)
 146     cd->cd_order[prec] = cd->cd_ordp++;
 147
 148   /* Reset cd_qualp to the highest precedence level that we've seen so
 149      far that can be qualified (CTF_PREC_BASE or CTF_PREC_POINTER).  */
 150
 151   if (prec > cd->cd_qualp && prec < CTF_PREC_ARRAY)
 152     cd->cd_qualp = prec;
 153
 154   /* C array declarators are ordered inside out so prepend them.  Also by
 155      convention qualifiers of base types precede the type specifier (e.g.
 156      const int vs. int const) even though the two forms are equivalent.  */
 157
 158   if (kind == CTF_K_ARRAY || (is_qual && prec == CTF_PREC_BASE))
 159     ctf_list_prepend (&cd->cd_nodes[prec], cdp);
 160   else
 161     ctf_list_append (&cd->cd_nodes[prec], cdp);
 162 }
 163
 164 _libctf_printflike_ (2, 3)
 165 void ctf_decl_sprintf (ctf_decl_t *cd, const char *format, ...)
 166 {
 167   va_list ap;
 168   char *str;
 169   int n;
 170
 171   if (cd->cd_enomem)
 172     return;
 173
 174   va_start (ap, format);
 175   n = vasprintf (&str, format, ap);
 176   va_end (ap);
 177
 178   if (n > 0)
 179     {
 180       char *newbuf;
 181       if ((newbuf = ctf_str_append (cd->cd_buf, str)) != NULL)
 182         cd->cd_buf = newbuf;
 183     }
 184
 185   /* Sticky error condition.  */
 186   if (n < 0 || cd->cd_buf == NULL)
 187     {
 188       free (cd->cd_buf);
 189       cd->cd_buf = NULL;
 190       cd->cd_enomem = 1;
 191     }
 192
 193   free (str);
 194 }
 195
 196 char *ctf_decl_buf (ctf_decl_t *cd)
 197 {
 198   return cd->cd_buf;
 199 }