X-Git-Url: https://ocean-lang.org/code/?p=ocean;a=blobdiff_plain;f=csrc%2Fparsergen.mdc;h=742996e16222854cecedd235f9449987cc6c5e08;hp=13b946fb0e992580c8c7b2d410a003415bb3eea3;hb=d7f2c9af259a43cbdb8def0ebe8040deed480848;hpb=2594d150e123c29949493c37c8b9c14aa6abe5a4 diff --git a/csrc/parsergen.mdc b/csrc/parsergen.mdc index 13b946f..742996e 100644 --- a/csrc/parsergen.mdc +++ b/csrc/parsergen.mdc @@ -151,11 +151,17 @@ those which don't. There are also "virtual" symbols used for precedence marking discussed later, and sometimes we won't know what type a symbol is yet. +To help with code safety it is possible to declare the terminal symbols. +If this is done, then any symbol used in a production that does not +appear in a head and is not declared is treated as an error. + ###### forward declarations enum symtype { Unknown, Virtual, Terminal, Nonterminal }; char *symtypes = "UVTN"; ###### symbol fields enum symtype type; +###### grammar fields + int terminals_declared; Symbols can be either `TK_ident` or `TK_mark`. They are saved in a table of known symbols and the resulting parser will report them as @@ -241,9 +247,10 @@ symbol, but its type might be `Unknown`. ### Data types and precedence. -Data type specification and precedence specification are both -introduced by a dollar sign at the start of the line. If the next -word is `LEFT`, `RIGHT` or `NON`, then the line specifies a +Data type specification, precedence specification, and declaration of +terminals are all introduced by a dollar sign at the start of the line. +If the next word is `LEFT`, `RIGHT` or `NON`, then the line specifies a +precedence, if it is `TERM` the the line declares terminals without precedence, otherwise it specifies a data type. The data type name is simply stored and applied to the head of all @@ -296,6 +303,7 @@ Subsequent lines introduce symbols with higher precedence. struct token t = token_next(ts); char *err; enum assoc assoc; + int term = 0; int found; if (t.num != TK_ident) { @@ -308,7 +316,10 @@ Subsequent lines introduce symbols with higher precedence. assoc = Right; else if (text_is(t.txt, "NON")) assoc = Non; - else { + else if (text_is(t.txt, "TERM")) { + term = 1; + g->terminals_declared = 1; + } else { g->current_type = t.txt; g->type_isref = isref; if (text_is(t.txt, "void")) @@ -326,7 +337,7 @@ Subsequent lines introduce symbols with higher precedence. goto abort; } - // This is a precedence line, need some symbols. + // This is a precedence or TERM line, need some symbols. found = 0; g->prec_levels += 1; t = token_next(ts); @@ -340,6 +351,10 @@ Subsequent lines introduce symbols with higher precedence. err = "$$ must be followed by a word"; goto abort; } + if (term) { + err = "Virtual symbols not permitted on $TERM line"; + goto abort; + } } else if (t.num != TK_ident && t.num != TK_mark) { err = "Illegal token in precedence line"; @@ -347,17 +362,19 @@ Subsequent lines introduce symbols with higher precedence. } s = sym_find(g, t.txt); if (s->type != Unknown) { - err = "Symbols in precedence line must not already be known."; + err = "Symbols in precedence/TERM line must not already be known."; goto abort; } s->type = type; - s->precedence = g->prec_levels; - s->assoc = assoc; + if (!term) { + s->precedence = g->prec_levels; + s->assoc = assoc; + } found += 1; t = token_next(ts); } if (found == 0) - err = "No symbols given on precedence line"; + err = "No symbols given on precedence/TERM line"; goto abort; return NULL; abort: @@ -391,14 +408,15 @@ be in one `code_node` of the literate code. The `}$` must be at the end of a line. Text in the code fragment will undergo substitutions where `$N` or -`$type == Unknown) - bs->type = Terminal; + if (bs->type == Unknown) { + if (!g->terminals_declared) + bs->type = Terminal; + } if (bs->type == Virtual) { err = "Virtual symbol not permitted in production"; goto abort; @@ -669,6 +689,21 @@ to produce errors that the parser is better positioned to handle. goto abort; } token_close(state); + if (g->terminals_declared) { + struct symbol *s; + int errs = 0; + for (s = g->syms; s; s = s->next) { + if (s->type != Unknown) + continue; + errs += 1; + fprintf(stderr, "Token %.*s not declared\n", + s->name.len, s->name.txt); + } + if (errs) { + free(g); + g = NULL; + } + } return g; abort: fprintf(stderr, "Error at line %d: %s\n", @@ -2135,13 +2170,105 @@ structure returned by a previous reduction. These pointers need to be cast to the appropriate type for each access. All this is handled in `gen_code`. -`gen_code` also allows symbol references to contain a '`<`' as in '`$<2`'. -This applied only to symbols with references (or pointers), not those with structures. -The `<` implies that the reference it being moved out, so the object will not be -automatically freed. This is equivalent to assigning `NULL` to the pointer. +`gen_code` also allows symbol references to contain a '`<`' as in +'`$<2`'. This is particularly useful for references (or pointers), but +can be used with structures too. The `<` implies that the value it +being moved out, so the object will not be automatically freed. It is +equivalent to assigning `NULL` to the pointer or filling a structure +with zeros. + +Instead of a number `N`, the `$` or `$<` can be followed by some letters +and possibly a number. A number by itself (other than zero) selects a +symbol from the body of the production. A sequence of letters selects +the shortest symbol in the body which contains those letters in the given +order. If a number follows the letters, then a later occurrence of +that symbol is chosen. So "`$AB2`" will refer to the structure attached +to the second occurrence of the shortest symbol which contains an `A` +followed by a `B`. If there is no unique shortest system, or if the +number given is too large, then the symbol reference is not transformed, +and will cause an error when the code is compiled. ###### functions + static int textchr(struct text t, char c, int s) + { + int i; + for (i = s; i < t.len; i++) + if (t.txt[i] == c) + return i; + return -1; + } + + static int subseq_match(char *seq, int slen, struct text name) + { + int st = 0; + while (slen > 0) { + st = textchr(name, *seq, st); + if (st < 0) + return 0; + slen -= 1; + seq += 1; + st += 1; + } + return 1; + } + + static int choose_sym(char **namep, int len, struct production *p) + { + char *name = *namep; + char *nam = name; + int namlen; + int n = 0; + int i, s, slen; + char c; + + c = *name; + while (len > 0 && + ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))) { + name += 1; + len -= 1; + c = *name; + } + namlen = name-nam; + while (len > 0 && (c >= '0' && c <= '9')) { + name += 1; + len -= 1; + n = n * 10 + (c - '0'); + c = *name; + } + if (namlen == 0) { + if (name == *namep) + return -1; + *namep = name; + return n; + } + slen = 0; s = -1; + for (i = 0; i < p->body_size; i++) { + if (!subseq_match(nam, namlen, p->body[i]->name)) + continue; + if (slen == 0 || p->body[i]->name.len < slen) + s = i; + if (s >= 0 && p->body[i] != p->body[s] && + p->body[i]->name.len == p->body[s]->name.len) + /* not unique, so s cannot be used */ + s = -1; + } + if (s < 0) + return -1; + if (n == 0); + n = 1; + for (i = 0; i < p->body_size; i++) + if (p->body[i] == p->body[s]) { + n -= 1; + if (n == 0) + break; + } + if (n > 1) + return -1; + *namep = name; + return i + 1; + } + static void gen_code(struct production *p, FILE *f, struct grammar *g) { char *c; @@ -2163,24 +2290,19 @@ automatically freed. This is equivalent to assigning `NULL` to the pointer. use = 1; c++; } - if (*c < '0' || *c > '9') { + n = choose_sym(&c, p->code.txt + p->code.len - c, p); + if (n < 0) { + fputc('$', f); if (use) fputc('<', f); fputc(*c, f); continue; } - n = *c - '0'; - while (c[1] >= '0' && c[1] <= '9') { - c += 1; - n = n * 10 + *c - '0'; - } if (n == 0) fprintf(f, "(*(struct %.*s*%s)ret)", p->head->struct_name.len, p->head->struct_name.txt, p->head->isref ? "*":""); - else if (n > p->body_size) - fprintf(f, "$%d", n); else if (p->body[n-1]->type == Terminal) fprintf(f, "(*(struct token *)body[%d])", n-1); @@ -2193,6 +2315,7 @@ automatically freed. This is equivalent to assigning `NULL` to the pointer. p->body[n-1]->isref ? "*":"", n-1); used[n-1] = use; } + c -= 1; } fputs("\n", f); for (i = 0; i < p->body_size; i++) { @@ -2779,8 +2902,12 @@ accepted the input and can finish. We return whatever `asn` was returned by reducing production zero. If we can neither shift nor reduce we have an error to handle. We pop -single entries off the stack until we can shift the `TK_error` symbol, then -drop input tokens until we find one we can shift into the new error state. +single entries off the stack until we can shift the `TK_error` symbol, +then drop input tokens until we find one we can shift into the new error +state. We need to ensure that something is dropped or shifted after an +error, or we could get into an infinite loop, only shifting in +`TK_error`, then reducing. So we track if there has been a shift since +the last error, and if not the next error always discards one token. When we find `TK_in` and `TK_out` tokens which report indents we need to handle them directly as the grammar cannot express what we want to @@ -2824,11 +2951,11 @@ in the thing that preceed: Here the NEWLINE will be shifted because nothing can be reduced until the `if` is seen. -When, during error handling, we discard token read in, we want to keep +When during error handling we discard tokens read in, we want to keep discarding until we see one that is recognised. If we had a full set -of LR(1) grammar states, this will mean looking in the look-ahead set, +of LR(1) grammar states, this would mean looking in the look-ahead set, but we don't keep a full look-ahead set. We only record the subset -that leads to SHIFT. We can, however, deduce the look-ahead set but +that leads to SHIFT. We can, however, deduce the look-ahead set by looking at the SHIFT subsets for all states that we can get to by reducing zero or more times. So we need a little function which checks if a given token is in any of these look-ahead sets. @@ -2860,6 +2987,7 @@ checks if a given token is in any of these look-ahead sets. struct parser p = { 0 }; struct token *tk = NULL; int accepted = 0; + int shift_since_err = 1; void *ret = NULL; shift(&p, TK_eof, 0, 1, NULL, states); @@ -2931,6 +3059,7 @@ checks if a given token is in any of these look-ahead sets. goto force_reduce; } if (shift(&p, tk->num, 0, tk->num == TK_newline, tk, states)) { + shift_since_err = 1; tk = NULL; parser_trace_action(trace, "Shift"); continue; @@ -2995,11 +3124,22 @@ checks if a given token is in any of these look-ahead sets. // no state accepted TK_error break; } + if (!shift_since_err) { + /* must discard at least one token to avoid + * infinite loop. + */ + if (tk->num == TK_eof) + break; + free(tk); + tk = tok_copy(token_next(tokens)); + } + shift_since_err = 0; tos = &p.stack[p.tos-1]; while (!in_lookahead(tk, states, tos->state) && tk->num != TK_eof) { free(tk); tk = tok_copy(token_next(tokens)); + shift_since_err = 1; if (tk->num == TK_in) indents += 1; if (tk->num == TK_out) {