[src/trunk]: src/usr.bin/xlint/lint1 lint: document why in GCC mode, C99 keyw...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0367ed364b47
branches:  trunk
changeset: 365884:0367ed364b47
user:      rillig <rillig%NetBSD.org@localhost>
date:      Sat Apr 30 20:43:16 2022 +0000

description:
lint: document why in GCC mode, C99 keywords are enabled

diffstat:

 usr.bin/xlint/lint1/lex.c |  36 +++++++++++++++++++++++++++---------
 1 files changed, 27 insertions(+), 9 deletions(-)

diffs (71 lines):

diff -r e4d4219923f6 -r 0367ed364b47 usr.bin/xlint/lint1/lex.c
--- a/usr.bin/xlint/lint1/lex.c Sat Apr 30 20:24:57 2022 +0000
+++ b/usr.bin/xlint/lint1/lex.c Sat Apr 30 20:43:16 2022 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: lex.c,v 1.125 2022/04/30 20:24:57 rillig Exp $ */
+/* $NetBSD: lex.c,v 1.126 2022/04/30 20:43:16 rillig Exp $ */
 
 /*
  * Copyright (c) 1996 Christopher G. Demetriou.  All Rights Reserved.
@@ -38,7 +38,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: lex.c,v 1.125 2022/04/30 20:24:57 rillig Exp $");
+__RCSID("$NetBSD: lex.c,v 1.126 2022/04/30 20:43:16 rillig Exp $");
 #endif
 
 #include <ctype.h>
@@ -105,7 +105,7 @@
                                 * T_TYPE or T_STRUCT_OR_UNION */
        tqual_t kw_tqual;       /* type qual. if kw_token T_QUAL */
        bool    kw_c90:1;       /* C90 keyword */
-       bool    kw_c99:1;       /* C99 keyword */
+       bool    kw_c99_or_c11:1; /* C99 or C11 keyword */
        bool    kw_gcc:1;       /* GCC keyword */
        bool    kw_attr:1;      /* GCC attribute */
        bool    kw_plain:1;     /* 'name' */
@@ -414,6 +414,29 @@
        symtab_add(sym);
 }
 
+static bool
+is_keyword_known(const struct keyword *kw)
+{
+
+       if ((kw->kw_c90 || kw->kw_c99_or_c11) && !allow_c90)
+               return false;
+
+       /*
+        * In the 1990s, GCC defined several keywords that were later
+        * incorporated into C99, therefore in GCC mode, all C99 keywords are
+        * made available.  The C11 keywords are made available as well, but
+        * there are so few that they don't matter practically.
+        */
+       if (allow_gcc)
+               return true;
+       if (kw->kw_gcc)
+               return false;
+
+       if (kw->kw_c99_or_c11 && !allow_c99)
+               return false;
+       return true;
+}
+
 /*
  * All keywords are written to the symbol table. This saves us looking
  * in an extra table for each name we found.
@@ -425,12 +448,7 @@
 
        end = keywords + sizeof(keywords) / sizeof(keywords[0]);
        for (kw = keywords; kw != end; kw++) {
-               if ((kw->kw_c90 || kw->kw_c99) && !allow_c90)
-                       continue;
-               /* FIXME: C99 and GCC are independent. */
-               if (kw->kw_c99 && !(allow_c99 || allow_gcc))
-                       continue;
-               if (kw->kw_gcc && !allow_gcc)
+               if (!is_keyword_known(kw))
                        continue;
                if (kw->kw_plain)
                        add_keyword(kw, false, false);