[src/trunk]: src/usr.bin/xlint/lint1 lint: document suppressed LDBL_MAX warni...

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

details:   https://anonhg.NetBSD.org/src/rev/16e799621384
branches:  trunk
changeset: 374254:16e799621384
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri Apr 14 18:42:31 2023 +0000

description:
lint: document suppressed LDBL_MAX warning more accurately

The crucial point is not that lint is cross-compiled but that tools/lint
is run on the usr.bin/xlint code, and in that situation, the platform
mismatch happens.

diffstat:

 usr.bin/xlint/lint1/tree.c |  29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

diffs (51 lines):

diff -r 417c0ed05cbf -r 16e799621384 usr.bin/xlint/lint1/tree.c
--- a/usr.bin/xlint/lint1/tree.c        Fri Apr 14 17:45:59 2023 +0000
+++ b/usr.bin/xlint/lint1/tree.c        Fri Apr 14 18:42:31 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tree.c,v 1.512 2023/04/12 19:09:48 rillig Exp $        */
+/*     $NetBSD: tree.c,v 1.513 2023/04/14 18:42:31 rillig Exp $        */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: tree.c,v 1.512 2023/04/12 19:09:48 rillig Exp $");
+__RCSID("$NetBSD: tree.c,v 1.513 2023/04/14 18:42:31 rillig Exp $");
 #endif
 
 #include <float.h>
@@ -1508,18 +1508,21 @@ floating_error_value(tspec_t t, ldbl_t l
        if (t == DOUBLE)
                return lv < 0 ? -DBL_MAX : DBL_MAX;
        /*
-        * When lint is compiled on x86_64 to check for sparc64, it uses the
-        * type 'long double' from x86_64, which is the Intel 80-bit format.
-        * The constant LDBL_MAX comes from the sparc64 preprocessor though
-        * and uses the IEEE-754-binary128 format, with the same exponent
-        * range but a wider mantissa.
+        * When NetBSD is cross-built in MKLINT=yes mode on x86_64 for
+        * sparc64, tools/lint checks this code while building usr.bin/xlint.
+        * In that situation, lint uses the preprocessor for sparc64, in which
+        * the type 'long double' is IEEE-754-binary128, affecting the macro
+        * LDBL_MAX below. The type 'long double', as well as the strtold
+        * implementation, comes from the host platform x86_64 though, where
+        * 'long double' consumes 128 bits as well but only uses 80 of them.
+        * The exponent range of the two 'long double' types is the same, but
+        * the maximum finite value differs due to the extended precision on
+        * sparc64.
         *
-        * To properly handle this situation, lint would have to implement the
-        * floating-point types in a platform-independent way, which is not
-        * worth the effort, given how few programs practically use 'long
-        * double'.
-        *
-        * This caveat only affects cross builds.
+        * To properly handle the data types of the target platform, lint
+        * would have to implement the floating-point types in a
+        * platform-independent way, which is not worth the effort, given how
+        * few programs practically use 'long double'.
         */
        /* LINTED 248: floating-point constant out of range */
        ldbl_t max = LDBL_MAX;