bc: handle BIN_FILE and LEX_BAD_CHAR errors at the site of detection

The most informative message can be generated at the location
where error is detected. The "error codes" are stupid:
print error meesage immediately, then just return "there was an error"
indicator.

All error codes will be converted. For now, converting these two.

For now, this and following changes will degrade error messages
quality. For example, file name and line number printouts may be lost.
This will be re-added later.

This change anlso fixes handling of invalid stdin input:
this used to cause interactive bc to exit:

....
>>> ς
bc: illegal character 0xcf
bc: illegal character 0x82
>>> _

function                                             old     new   delta
bc_error                                               -      42     +42
bc_lex_token                                        1333    1369     +36
dc_lex_token                                         675     695     +20
bc_read_line                                         311     325     +14
bc_num_a                                             456     454      -2
bc_err_msgs                                          188     184      -4
bc_num_ulong                                          95      85     -10
bc_vm_run                                           1984    1955     -29
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/4 up/down: 112/-45)            Total: 67 bytes
   text	   data	    bss	    dec	    hex	filename
 987828	    485	   7296	 995609	  f3119	busybox_old
 987929	    485	   7296	 995710	  f317e	busybox_unstripped

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

miscutils/bc.c

@@ -169,13 +169,14 @@
 
 typedef enum BcStatus {
 	BC_STATUS_SUCCESS,
+	BC_STATUS_FAILURE,
 
 //	BC_STATUS_ALLOC_ERR,
 //	BC_STATUS_INPUT_EOF,
-	BC_STATUS_BIN_FILE,
+//	BC_STATUS_BIN_FILE,
 //	BC_STATUS_PATH_IS_DIR,
 
-	BC_STATUS_LEX_BAD_CHAR,
+//	BC_STATUS_LEX_BAD_CHAR,
 	BC_STATUS_LEX_NO_STRING_END,
 	BC_STATUS_LEX_NO_COMMENT_END,
 	BC_STATUS_LEX_EOF,
@@ -239,12 +240,13 @@ typedef enum BcStatus {
 // Keep enum above and messages below in sync!
 static const char *const bc_err_msgs[] = {
 	NULL,
+	"",
 //	"memory allocation error",
 //	"I/O error",
-	"file is not text:",
+//	"file is not text:",
 //	"path is a directory:",
 
-	"bad character",
+//	"bad character",
 	"string end could not be found",
 	"comment end could not be found",
 	"end of file",
@@ -321,8 +323,6 @@ typedef struct BcVec {
 
 #define bc_map_init(v) (bc_vec_init((v), sizeof(BcId), bc_id_free))
 
-#define BC_READ_BIN_CHAR(c) ((((c) < ' ' && !isspace((c))) || (c) > '~'))
-
 typedef signed char BcDig;
 
 typedef struct BcNum {
@@ -1138,6 +1138,18 @@ static void quit(void)
 	exit(0);
 }
 
+static int bc_error(const char *fmt, ...)
+{
+	va_list p;
+
+	va_start(p, fmt);
+	bb_verror_msg(fmt, p, NULL);
+	va_end(p);
+	if (!G.ttyin)
+		exit(1);
+	return BC_STATUS_FAILURE;
+}
+
 static void bc_vec_grow(BcVec *v, size_t n)
 {
 	size_t cap = v->cap * 2;
@@ -1289,54 +1301,63 @@ static size_t bc_map_index(const BcVec *v, const void *ptr)
 
 static BcStatus bc_read_line(BcVec *vec, const char *prompt)
 {
-	int i;
+	bool bad_chars;
-	signed char c;
 
-	bc_vec_npop(vec, vec->len);
-
-	fflush_and_check();
-#if ENABLE_FEATURE_BC_SIGNALS
-	if (bb_got_signal) { // ^C was pressed
- intr:
-		bb_got_signal = 0; // resets G_interrupt to zero
-		fputs(IS_BC
-			? "\ninterrupt (type \"quit\" to exit)\n"
-			: "\ninterrupt (type \"q\" to exit)\n"
-			, stderr);
-	}
-#endif
-	if (G.ttyin && !G_posix)
-		fputs(prompt, stderr);
-	fflush_and_check();
-
-#if ENABLE_FEATURE_BC_SIGNALS
-	errno = 0;
-#endif
 	do {
-		i = fgetc(stdin);
+		int i;
+		char c;
 
-		if (i == EOF) {
+		bad_chars = 0;
+		bc_vec_npop(vec, vec->len);
+
+		fflush_and_check();
 #if ENABLE_FEATURE_BC_SIGNALS
-			// Both conditions appear simultaneously, check both just in case
+		if (bb_got_signal) { // ^C was pressed
-			if (errno == EINTR || bb_got_signal) {
+ intr:
-				// ^C was pressed
+			bb_got_signal = 0; // resets G_interrupt to zero
-				clearerr(stdin);
+			fputs(IS_BC
-				goto intr;
+				? "\ninterrupt (type \"quit\" to exit)\n"
-			}
+				: "\ninterrupt (type \"q\" to exit)\n"
-#endif
+				, stderr);
-			if (ferror(stdin))
-				quit(); // this emits error message
-			G.eof = 1;
-			// Note: EOF does not append '\n', therefore:
-			// printf 'print 123\n' | bc - works
-			// printf 'print 123' | bc   - fails (syntax error)
-			break;
 		}
+#endif
+		if (G.ttyin && !G_posix)
+			fputs(prompt, stderr);
 
-		c = (signed char) i;
+#if ENABLE_FEATURE_BC_SIGNALS
-		if (i > UCHAR_MAX || BC_READ_BIN_CHAR(c)) return BC_STATUS_BIN_FILE;
+		errno = 0;
-		bc_vec_push(vec, &c);
+#endif
-	} while (c != '\n');
+		do {
+			i = fgetc(stdin);
+			if (i == EOF) {
+#if ENABLE_FEATURE_BC_SIGNALS
+				// Both conditions appear simultaneously, check both just in case
+				if (errno == EINTR || bb_got_signal) {
+					// ^C was pressed
+					clearerr(stdin);
+					goto intr;
+				}
+#endif
+				if (ferror(stdin))
+					quit(); // this emits error message
+				G.eof = 1;
+				// Note: EOF does not append '\n', therefore:
+				// printf 'print 123\n' | bc - works
+				// printf 'print 123' | bc   - fails (syntax error)
+				break;
+			}
+
+			if ((i < ' ' && i != '\t' && i != '\r' && i != '\n') // also allow '\v' '\f'?
+			 || i > 0x7e
+			) {
+				// Bad chars on this line, ignore entire line
+				bc_error("illegal character 0x%02x", i);
+				bad_chars = 1;
+			}
+			c = (char) i;
+			bc_vec_push(vec, &c);
+		} while (i != '\n');
+	} while (bad_chars);
 
 	bc_vec_pushByte(vec, '\0');
 
@@ -1352,7 +1373,10 @@ static char* bc_read_file(const char *path)
 	buf = xmalloc_open_read_close(path, &size);
 
 	for (i = 0; i < size; ++i) {
-		if (BC_READ_BIN_CHAR(buf[i])) {
+		char c = buf[i];
+		if ((c < ' ' && c != '\t' && c != '\r' && c != '\n') // also allow '\v' '\f'?
+		 || c > 0x7e
+		) {
 			free(buf);
 			buf = NULL;
 			break;
@@ -3162,7 +3186,7 @@ static BcStatus bc_lex_token(BcLex *l)
 			}
 			else {
 				l->t.t = BC_LEX_INVALID;
-				s = BC_STATUS_LEX_BAD_CHAR;
+				s = bc_error("bad character '%c'", '&');
 			}
 
 			break;
@@ -3291,7 +3315,7 @@ static BcStatus bc_lex_token(BcLex *l)
 				++l->i;
 			}
 			else
-				s = BC_STATUS_LEX_BAD_CHAR;
+				s = bc_error("bad character '%c'", c);
 			break;
 		}
 
@@ -3353,7 +3377,7 @@ static BcStatus bc_lex_token(BcLex *l)
 			}
 			else {
 				l->t.t = BC_LEX_INVALID;
-				s = BC_STATUS_LEX_BAD_CHAR;
+				s = bc_error("bad character '%c'", c);
 			}
 
 			break;
@@ -3362,7 +3386,7 @@ static BcStatus bc_lex_token(BcLex *l)
 		default:
 		{
 			l->t.t = BC_LEX_INVALID;
-			s = BC_STATUS_LEX_BAD_CHAR;
+			s = bc_error("bad character '%c'", c);
 			break;
 		}
 	}
@@ -3473,7 +3497,7 @@ static BcStatus dc_lex_token(BcLex *l)
 			else if (c2 == '>')
 				l->t.t = BC_LEX_OP_REL_GE;
 			else
-				return BC_STATUS_LEX_BAD_CHAR;
+				return bc_error("bad character '%c'", c);
 
 			++l->i;
 			break;
@@ -3490,7 +3514,7 @@ static BcStatus dc_lex_token(BcLex *l)
 			if (isdigit(l->buf[l->i]))
 				s = bc_lex_number(l, c);
 			else
-				s = BC_STATUS_LEX_BAD_CHAR;
+				s = bc_error("bad character '%c'", c);
 			break;
 		}
 
@@ -3524,7 +3548,7 @@ static BcStatus dc_lex_token(BcLex *l)
 		default:
 		{
 			l->t.t = BC_LEX_INVALID;
-			s = BC_STATUS_LEX_BAD_CHAR;
+			s = bc_error("bad character '%c'", c);
 			break;
 		}
 	}
@@ -6938,7 +6962,7 @@ static BcStatus bc_vm_file(const char *file)
 
 	G.prog.file = file;
 	data = bc_read_file(file);
-	if (!data) return bc_vm_error(BC_STATUS_BIN_FILE, file, 0);
+	if (!data) return bc_error("file '%s' is not text", file);
 
 	bc_lex_file(&G.prs.l, file);
 	s = bc_vm_process(data);
@@ -7021,8 +7045,6 @@ static BcStatus bc_vm_stdin(void)
 		bc_vec_npop(&buffer, buffer.len);
 	}
 
-	if (s == BC_STATUS_BIN_FILE) s = bc_vm_error(s, G.prs.l.f, 0);
-
 	if (str)
 		s = bc_vm_error(BC_STATUS_LEX_NO_STRING_END, G.prs.l.f,
 		                G.prs.l.line);