libctf/ctf-decl.c

   1 /* C declarator syntax glue.
   2    Copyright (C) 2019-2022 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   free (cd->cd_buf);
  72 }
  73
  74 void
  75 ctf_decl_push (ctf_decl_t *cd, ctf_dict_t *fp, ctf_id_t type)
  76 {
  77   ctf_decl_node_t *cdp;
  78   ctf_decl_prec_t prec;
  79   uint32_t kind, n = 1;
  80   int is_qual = 0;
  81
  82   const ctf_type_t *tp;
  83   ctf_arinfo_t ar;
  84
  85   if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
  86     {
  87       cd->cd_err = fp->ctf_errno;
  88       return;
  89     }
  90
  91   switch (kind = LCTF_INFO_KIND (fp, tp->ctt_info))
  92     {
  93     case CTF_K_ARRAY:
  94       (void) ctf_array_info (fp, type, &ar);
  95       ctf_decl_push (cd, fp, ar.ctr_contents);
  96       n = ar.ctr_nelems;
  97       prec = CTF_PREC_ARRAY;
  98       break;
  99
 100     case CTF_K_TYPEDEF:
 101       if (ctf_strptr (fp, tp->ctt_name)[0] == '\0')
 102         {
 103           ctf_decl_push (cd, fp, tp->ctt_type);
 104           return;
 105         }
 106       prec = CTF_PREC_BASE;
 107       break;
 108
 109     case CTF_K_FUNCTION:
 110       ctf_decl_push (cd, fp, tp->ctt_type);
 111       prec = CTF_PREC_FUNCTION;
 112       break;
 113
 114     case CTF_K_POINTER:
 115       ctf_decl_push (cd, fp, tp->ctt_type);
 116       prec = CTF_PREC_POINTER;
 117       break;
 118
 119     case CTF_K_SLICE:
 120       /* Slices themselves have no print representation and should not appear in
 121          the decl stack.  */
 122       ctf_decl_push (cd, fp, ctf_type_reference (fp, type));
 123       return;
 124
 125     case CTF_K_VOLATILE:
 126     case CTF_K_CONST:
 127     case CTF_K_RESTRICT:
 128       ctf_decl_push (cd, fp, tp->ctt_type);
 129       prec = cd->cd_qualp;
 130       is_qual++;
 131       break;
 132
 133     default:
 134       prec = CTF_PREC_BASE;
 135     }
 136
 137   if ((cdp = malloc (sizeof (ctf_decl_node_t))) == NULL)
 138     {
 139       cd->cd_err = EAGAIN;
 140       return;
 141     }
 142
 143   cdp->cd_type = type;
 144   cdp->cd_kind = kind;
 145   cdp->cd_n = n;
 146
 147   if (ctf_list_next (&cd->cd_nodes[prec]) == NULL)
 148     cd->cd_order[prec] = cd->cd_ordp++;
 149
 150   /* Reset cd_qualp to the highest precedence level that we've seen so
 151      far that can be qualified (CTF_PREC_BASE or CTF_PREC_POINTER).  */
 152
 153   if (prec > cd->cd_qualp && prec < CTF_PREC_ARRAY)
 154     cd->cd_qualp = prec;
 155
 156   /* By convention qualifiers of base types precede the type specifier (e.g.
 157      const int vs. int const) even though the two forms are equivalent.  */
 158
 159   if (is_qual && prec == CTF_PREC_BASE)
 160     ctf_list_prepend (&cd->cd_nodes[prec], cdp);
 161   else
 162     ctf_list_append (&cd->cd_nodes[prec], cdp);
 163 }
 164
 165 _libctf_printflike_ (2, 3)
 166 void ctf_decl_sprintf (ctf_decl_t *cd, const char *format, ...)
 167 {
 168   va_list ap;
 169   char *str;
 170   int n;
 171
 172   if (cd->cd_enomem)
 173     return;
 174
 175   va_start (ap, format);
 176   n = vasprintf (&str, format, ap);
 177   va_end (ap);
 178
 179   if (n > 0)
 180     {
 181       char *newbuf;
 182       if ((newbuf = ctf_str_append (cd->cd_buf, str)) != NULL)
 183         cd->cd_buf = newbuf;
 184     }
 185
 186   /* Sticky error condition.  */
 187   if (n < 0 || cd->cd_buf == NULL)
 188     {
 189       free (cd->cd_buf);
 190       cd->cd_buf = NULL;
 191       cd->cd_enomem = 1;
 192     }
 193
 194   free (str);
 195 }
 196
 197 char *ctf_decl_buf (ctf_decl_t *cd)
 198 {
 199   char *buf = cd->cd_buf;
 200   cd->cd_buf = NULL;
 201   return buf;
 202 }