[src/trunk]: src/usr.bin/xlint/lint1 lint: replace array access with function...

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

details:   https://anonhg.NetBSD.org/src/rev/8738bcd4db62
branches:  trunk
changeset: 1021742:8738bcd4db62
user:      rillig <rillig%NetBSD.org@localhost>
date:      Tue Jun 15 20:46:45 2021 +0000

description:
lint: replace array access with function calls

First and foremost, the test d_c99_complex_split accessed the array
qlmasks out-of-bounds, with an index of 128 for the type 'double
_Complex'.  This invoked undefined behavior since the maximum allowed
index was 64.

Replacing the raw array accesses with function calls allows for bounds
checks to catch these errors early.

Determining the value bits for a 'double _Complex' does not make sense
at all since it is not an integer type.  This means that lint didn't
handle these types correctly for several years.  Support for int128_t
has been added in inittyp.c 1.12 from 2018-09-07, support for _Complex
has been added in inittyp.c 1.9 from 2008-04-26.

Determining the value bits for an int128_t would make sense, but the
unit tests don't contain examples for this type since at the moment all
unit tests must produce the same results on 32-bit and 64-bit platforms,
and the 32-bit platforms don't support int128_t.

diffstat:

 usr.bin/xlint/lint1/externs1.h |   3 +--
 usr.bin/xlint/lint1/lex.c      |  38 ++++++++------------------------------
 usr.bin/xlint/lint1/lint1.h    |  26 +++++++++++++++++++++++++-
 usr.bin/xlint/lint1/tree.c     |  12 ++++++------
 4 files changed, 40 insertions(+), 39 deletions(-)

diffs (192 lines):

diff -r 0fdec32e6565 -r 8738bcd4db62 usr.bin/xlint/lint1/externs1.h
--- a/usr.bin/xlint/lint1/externs1.h    Tue Jun 15 18:54:34 2021 +0000
+++ b/usr.bin/xlint/lint1/externs1.h    Tue Jun 15 20:46:45 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: externs1.h,v 1.108 2021/04/18 17:36:18 rillig Exp $    */
+/*     $NetBSD: externs1.h,v 1.109 2021/06/15 20:46:45 rillig Exp $    */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -75,7 +75,6 @@
 extern bool    in_system_header;
 extern symt_t  symtyp;
 extern FILE    *yyin;
-extern uint64_t qbmasks[], qlmasks[], qumasks[];
 
 extern void    initscan(void);
 extern int     msb(int64_t, tspec_t, int);
diff -r 0fdec32e6565 -r 8738bcd4db62 usr.bin/xlint/lint1/lex.c
--- a/usr.bin/xlint/lint1/lex.c Tue Jun 15 18:54:34 2021 +0000
+++ b/usr.bin/xlint/lint1/lex.c Tue Jun 15 20:46:45 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: lex.c,v 1.36 2021/05/03 08:03:45 rillig Exp $ */
+/* $NetBSD: lex.c,v 1.37 2021/06/15 20:46:45 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 1.36 2021/05/03 08:03:45 rillig Exp $");
+__RCSID("$NetBSD: lex.c,v 1.37 2021/06/15 20:46:45 rillig Exp $");
 #endif
 
 #include <ctype.h>
@@ -250,15 +250,6 @@
 /* Symbol table */
 static sym_t   *symtab[HSHSIZ1];
 
-/* bit i of the entry with index i is set */
-uint64_t qbmasks[64];
-
-/* least significant i bits are set in the entry with index i */
-uint64_t qlmasks[64 + 1];
-
-/* least significant i bits are not set in the entry with index i */
-uint64_t qumasks[64 + 1];
-
 /* free list for sbuf structures */
 static sbuf_t   *sbfrlst;
 
@@ -321,8 +312,6 @@
 initscan(void)
 {
        struct  kwtab *kw;
-       size_t  i;
-       uint64_t uq;
 
        for (kw = kwtab; kw->kw_name != NULL; kw++) {
                if ((kw->kw_c89 || kw->kw_c99) && tflag)
@@ -335,16 +324,6 @@
                add_keyword(kw, 2);
                add_keyword(kw, 4);
        }
-
-       /* initialize bit-masks for quads */
-       for (i = 0; i < 64; i++) {
-               qbmasks[i] = (uint64_t)1 << i;
-               uq = ~(uint64_t)0 << i;
-               qumasks[i] = uq;
-               qlmasks[i] = ~uq;
-       }
-       qumasks[i] = 0;
-       qlmasks[i] = ~(uint64_t)0;
 }
 
 /*
@@ -715,7 +694,7 @@
 
        if (len <= 0)
                len = size_in_bits(t);
-       return (q & qbmasks[len - 1]) != 0 ? 1 : 0;
+       return (q & bit(len - 1)) != 0 ? 1 : 0;
 }
 
 /*
@@ -724,16 +703,15 @@
 int64_t
 xsign(int64_t q, tspec_t t, int len)
 {
+       uint64_t vbits;
 
        if (len <= 0)
                len = size_in_bits(t);
 
-       if (t == PTR || is_uinteger(t) || !sign(q, t, len)) {
-               q &= qlmasks[len];
-       } else {
-               q |= qumasks[len];
-       }
-       return q;
+       vbits = value_bits(len);
+       return t == PTR || is_uinteger(t) || !sign(q, t, len)
+           ? q & vbits
+           : q | ~vbits;
 }
 
 /*
diff -r 0fdec32e6565 -r 8738bcd4db62 usr.bin/xlint/lint1/lint1.h
--- a/usr.bin/xlint/lint1/lint1.h       Tue Jun 15 18:54:34 2021 +0000
+++ b/usr.bin/xlint/lint1/lint1.h       Tue Jun 15 20:46:45 2021 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: lint1.h,v 1.101 2021/05/15 19:12:14 rillig Exp $ */
+/* $NetBSD: lint1.h,v 1.102 2021/06/15 20:46:45 rillig Exp $ */
 
 /*
  * Copyright (c) 1996 Christopher G. Demetriou.  All Rights Reserved.
@@ -531,3 +531,27 @@
 {
        return tn != NULL && tn->tn_op == CON && is_nonzero_val(tn->tn_val);
 }
+
+static inline uint64_t
+bit(unsigned i)
+{
+       lint_assert(i < 64);
+       return (uint64_t)1 << i;
+}
+
+static inline uint64_t
+value_bits(unsigned bitsize)
+{
+       lint_assert(bitsize > 0);
+
+       /* for long double (80 or 128), double _Complex (128) */
+       /*
+        * XXX: double _Complex does not have 128 bits of precision,
+        * therefore it should never be necessary to query the value bits
+        * of such a type; see d_c99_complex_split.c to trigger this case.
+        */
+       if (bitsize >= 64)
+               return ~((uint64_t)0);
+
+       return ~(~(uint64_t)0 << bitsize);
+}
diff -r 0fdec32e6565 -r 8738bcd4db62 usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Tue Jun 15 18:54:34 2021 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Tue Jun 15 20:46:45 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.286 2021/06/15 18:23:39 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.287 2021/06/15 20:46:45 rillig Exp $        */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID) && !defined(lint)
-__RCSID("$NetBSD: tree.c,v 1.286 2021/06/15 18:23:39 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.287 2021/06/15 20:46:45 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -2203,7 +2203,7 @@
                                    const type_t *tp, op_t op)
 {
        if (nsz > osz &&
-           (nv->v_quad & qbmasks[osz - 1]) != 0 &&
+           (nv->v_quad & bit(osz - 1)) != 0 &&
            (nv->v_quad & xmask) != xmask) {
                /* extra bits set to 0 in conversion of '%s' to '%s', ... */
                warning(309, type_name(gettyp(ot)),
@@ -2315,8 +2315,8 @@
 
        osz = size_in_bits(ot);
        nsz = tp->t_bitfield ? tp->t_flen : size_in_bits(nt);
-       xmask = qlmasks[nsz] ^ qlmasks[osz];
-       xmsk1 = qlmasks[nsz] ^ qlmasks[osz - 1];
+       xmask = value_bits(nsz) ^ value_bits(osz);
+       xmsk1 = value_bits(nsz) ^ value_bits(osz - 1);
        /*
         * For bitwise operations we are not interested in the
         * value, but in the bits itself.
@@ -2940,7 +2940,7 @@
        if (modtab[tn->tn_op].m_binary)
                ur = sr = tn->tn_right->tn_val->v_quad;
 
-       mask = qlmasks[size_in_bits(t)];
+       mask = value_bits(size_in_bits(t));
        ovfl = false;
 
        switch (tn->tn_op) {