4f27503a1
Denys Vlasenko
2021-06-29
Subject
awk: get rid of "move name one char back" trick in next_token()
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editors/awk.c+27 -27
| @@ -535,6 +535,7 @@ struct globals { | |
| var *Fields; | |
| nvblock *g_cb; | |
| char *g_pos; | |
| + | char g_saved_ch; |
| smallint icase; | |
| smallint exiting; | |
| smallint nextrec; | |
| @@ -599,6 +600,7 @@ struct globals2 { | |
| #define Fields (G1.Fields ) | |
| #define g_cb (G1.g_cb ) | |
| #define g_pos (G1.g_pos ) | |
| + | #define g_saved_ch (G1.g_saved_ch ) |
| #define icase (G1.icase ) | |
| #define exiting (G1.exiting ) | |
| #define nextrec (G1.nextrec ) | |
| @@ -1125,6 +1127,10 @@ static uint32_t next_token(uint32_t expected) | |
| t_info = save_info; | |
| } else { | |
| p = g_pos; | |
| + | if (g_saved_ch != '\0') { |
| + | *p = g_saved_ch; |
| + | g_saved_ch = '\0'; |
| + | } |
| readnext: | |
| p = skip_spaces(p); | |
| g_lineno = t_lineno; | |
| @@ -1183,6 +1189,8 @@ static uint32_t next_token(uint32_t expected) | |
| tc = TC_NUMBER; | |
| debug_printf_parse("%s: token found:%f TC_NUMBER\n", __func__, t_double); | |
| } else { | |
| + | char *end_of_name; |
| + | |
| if (*p == '\n') | |
| t_lineno++; | |
| @@ -1219,16 +1227,14 @@ static uint32_t next_token(uint32_t expected) | |
| if (!isalnum_(*p)) | |
| syntax_error(EMSG_UNEXP_TOKEN); /* no */ | |
| /* yes */ | |
| - | /* "move name one char back" trick: we need a byte for NUL terminator */ |
| - | /* NB: this results in argv[i][-1] being used (!!!) in e.g. "awk -e 'NAME'" case */ |
| - | t_string = --p; |
| - | while (isalnum_(*++p)) { |
| - | p[-1] = *p; |
| - | } |
| - | p[-1] = '\0'; |
| + | t_string = p; |
| + | while (isalnum_(*p)) |
| + | p++; |
| + | end_of_name = p; |
| tc = TC_VARIABLE; | |
| /* also consume whitespace between functionname and bracket */ | |
| if (!(expected & TC_VARIABLE) || (expected & TC_ARRAY)) | |
| + | //TODO: why if variable can be here (but not array ref), skipping is not allowed? Example where it matters? |
| p = skip_spaces(p); | |
| if (*p == '(') { | |
| p++; | |
| @@ -1240,7 +1246,19 @@ static uint32_t next_token(uint32_t expected) | |
| debug_printf_parse("%s: token found:'%s' TC_ARRAY\n", __func__, t_string); | |
| } else { | |
| debug_printf_parse("%s: token found:'%s' TC_VARIABLE\n", __func__, t_string); | |
| + | if (end_of_name == p) { |
| + | /* there is no space for trailing NUL in t_string! |
| + | * We need to save the char we are going to NUL. |
| + | * (we'll use it in future call to next_token()) |
| + | */ |
| + | g_saved_ch = *end_of_name; |
| + | // especially pathological example is V="abc"; V.2 - it's V concatenated to .2 |
| + | // (it evaluates to "abc0.2"). Because of this case, we can't simply cache |
| + | // '.' and analyze it later: we also have to *store it back* in next |
| + | // next_token(), in order to give my_strtod() the undamaged ".2" string. |
| + | } |
| } | |
| + | *end_of_name = '\0'; /* terminate t_string */ |
| } | |
| token_found: | |
| g_pos = p; | |
| @@ -3420,38 +3438,20 @@ int awk_main(int argc UNUSED_PARAM, char **argv) | |
| g_progname = llist_pop(&list_f); | |
| fd = xopen_stdin(g_progname); | |
| - | /* 1st byte is reserved for "move name one char back" trick in next_token */ |
| - | i = 1; |
| - | s = NULL; |
| - | for (;;) { |
| - | int sz; |
| - | s = xrealloc(s, i + 1000); |
| - | sz = safe_read(fd, s + i, 1000); |
| - | if (sz <= 0) |
| - | break; |
| - | i += sz; |
| - | } |
| - | s = xrealloc(s, i + 1); /* trim unused 999 bytes */ |
| - | s[i] = '\0'; |
| + | s = xmalloc_read(fd, NULL); /* it's NUL-terminated */ |
| close(fd); | |
| - | parse_program(s + 1); |
| + | parse_program(s); |
| free(s); | |
| } | |
| g_progname = "cmd. line"; | |
| #if ENABLE_FEATURE_AWK_GNU_EXTENSIONS | |
| while (list_e) { | |
| - | /* NB: "move name one char back" trick in next_token |
| - | * can use argv[i][-1] here. |
| - | */ |
| parse_program(llist_pop(&list_e)); | |
| } | |
| #endif | |
| if (!(opt & (OPT_f | OPT_e))) { | |
| if (!*argv) | |
| bb_show_usage(); | |
| - | /* NB: "move name one char back" trick in next_token |
| - | * can use argv[i][-1] here. |
| - | */ |
| parse_program(*argv++); | |
| } | |