bc: add code to detect errors like "print 1 print 2"

function                                             old     new   delta
zbc_vm_process                                       831     925     +94
zbc_program_exec                                    3964    3976     +12
zdc_program_execStr                                  506     512      +6
zbc_lex_next                                        2161    2167      +6
zbc_program_assign                                   419     424      +5
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/0 up/down: 123/0)             Total: 123 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 39 insertions, 10 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 7c8edcf33..8b44d4425 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -711,6 +711,7 @@ dc_LEX_to_INST[] = { // starts at XC_LEX_OP_POWER       // corresponding XC/DC_L
 
 typedef struct BcLex {
         const char *buf;
+        const char *lex_next_at; // last lex_next() was called at this string
         size_t i;
         size_t line;
         size_t len;
@@ -2990,9 +2991,11 @@ static BC_STATUS zbc_lex_next(BcLex *l)
                         }
                         // here it's guaranteed that l->i is below l->len
                 }
+                l->lex_next_at = l->buf + l->i;
                 dbg_lex("next string to parse:'%.*s'",
-                        (int)(strchrnul(l->buf + l->i, '\n') - (l->buf + l->i)),
-                        l->buf + l->i);
+                        (int)(strchrnul(l->lex_next_at, '\n') - l->lex_next_at),
+                        l->lex_next_at
+                );
                 if (IS_BC) {
                         IF_BC(s = zbc_lex_token(l));
                 } else {
@@ -6756,13 +6759,38 @@ static BC_STATUS zbc_vm_process(const char *text)
 
                 dbg_lex("%s:%d G.prs.l.lex:%d, parsing...", __func__, __LINE__, G.prs.l.lex);
                 if (IS_BC) {
-// FIXME: "eating" of stmt delimiters is coded inconsistently
-// (sometimes zbc_parse_stmt() eats the delimiter, sometimes don't),
-// which causes bugs such as "print 1 print 2" erroneously accepted,
-// or "print 1 else 2" detecting parse error only after executing
-// "print 1" part.
-                        IF_BC(s = zbc_parse_stmt_or_funcdef(&G.prs));
+#if ENABLE_BC
+                        s = zbc_parse_stmt_or_funcdef(&G.prs);
+                        if (s) goto err;
+
+                        // Check that next token is not bogus, and skip over
+                        // stmt delimiter(s) - newlines and semicolons
+                        s = 1; // s == 1 on first iteration only
+                        for (;;) {
+                                if (G.prs.l.lex == XC_LEX_EOF)
+                                        goto execute; // this goto avoids resetting 's' to zero
+                                if (G.prs.l.lex != BC_LEX_SCOLON
+                                 && G.prs.l.lex != XC_LEX_NLINE
+                                ) {
+                                        const char *err_at;
+                                        // Not newline and not semicolon
+                                        if (s == 0) // saw at least one NL/semicolon before it?
+                                                break; // yes, good
+//TODO: commolalize for other parse errors:
+                                        err_at = G.prs.l.lex_next_at ? G.prs.l.lex_next_at : "UNKNOWN";
+                                        bc_error_fmt("bad statement terminator at '%.*s'",
+                                                (int)(strchrnul(err_at, '\n') - err_at),
+                                                err_at
+                                        );
+                                        goto err;
+                                }
+                                // NL or semicolon: skip it, set s = 0, repeat
+                                s = zbc_lex_next(&G.prs.l);
+                                if (s) goto err;
+                        }
+#endif
                 } else {
+#if ENABLE_DC
                         // Most of dc parsing assumes all whitespace,
                         // including '\n', is eaten.
                         while (G.prs.l.lex == XC_LEX_NLINE) {
@@ -6771,14 +6799,15 @@ static BC_STATUS zbc_vm_process(const char *text)
                                 if (G.prs.l.lex == XC_LEX_EOF)
                                         goto done;
                         }
-                        IF_DC(s = zdc_parse_expr(&G.prs));
+                        s = zdc_parse_expr(&G.prs);
+#endif
                 }
                 if (s || G_interrupt) {
  err:
                         bc_parse_reset(&G.prs); // includes bc_program_reset()
                         RETURN_STATUS(BC_STATUS_FAILURE);
                 }
-
+ IF_BC(execute:)
                 dbg_lex("%s:%d executing...", __func__, __LINE__);
                 s = zbc_program_exec();
                 if (s) {