From: Ondřej Surý <ondrej@isc.org>
Date: Tue, 5 Aug 2025 06:19:20 +0000 (+0200)
Subject: Require the __builtin functions unconditionally
X-Git-Tag: v9.21.12~23^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=40fda03e5094a416cd864aaaf30883d9f4ac8e9f;p=thirdparty%2Fbind9.git

Require the __builtin functions unconditionally

Currently following __builtin functions are used:

    __builtin_add_overflow
    __builtin_mul_overflow
    __builtin_prefetch
    __builtin_sub_overflow
    __builtin_unreachable

These are generally available on our supported platform, and also we use
some of these unconditionally anyway in qp.c.  Thus make the support for
these functions mandatory so we fail early in the 'setup' step.
---

diff --git a/lib/isc/include/isc/overflow.h b/lib/isc/include/isc/overflow.h
index 62727513ad2..bd8e4eec737 100644
--- a/lib/isc/include/isc/overflow.h
+++ b/lib/isc/include/isc/overflow.h
@@ -39,29 +39,11 @@
  *	INSIST(!overflow);
  */
 
-#if HAVE_BUILTIN_MUL_OVERFLOW
 #define ISC_OVERFLOW_MUL(a, b, cp) __builtin_mul_overflow(a, b, cp)
-#else
-#define ISC_OVERFLOW_MUL(a, b, cp)                                           \
-	((ISC_OVERFLOW_UINT_MAX(a) / (b) > (a)) ? (*(cp) = (a) * (b), false) \
-						: true)
-#endif
 
-#if HAVE_BUILTIN_ADD_OVERFLOW
 #define ISC_OVERFLOW_ADD(a, b, cp) __builtin_add_overflow(a, b, cp)
-#else
-#define ISC_OVERFLOW_ADD(a, b, cp)                                           \
-	((ISC_OVERFLOW_UINT_MAX(a) - (b) > (a)) ? (*(cp) = (a) + (b), false) \
-						: true)
-#endif
 
-#if HAVE_BUILTIN_SUB_OVERFLOW
 #define ISC_OVERFLOW_SUB(a, b, cp) __builtin_sub_overflow(a, b, cp)
-#else
-#define ISC_OVERFLOW_SUB(a, b, cp)                                           \
-	((ISC_OVERFLOW_UINT_MIN(a) + (b) < (a)) ? (*(cp) = (a) - (b), false) \
-						: true)
-#endif
 
 #define ISC_CHECKED_MUL(a, b)                                      \
 	({                                                         \
diff --git a/meson.build b/meson.build
index d0ae062092b..133e6d1e8fa 100644
--- a/meson.build
+++ b/meson.build
@@ -316,12 +316,14 @@ endif
 
 foreach fn : [
     '__builtin_add_overflow',
+    '__builtin_expect',
     '__builtin_mul_overflow',
+    '__builtin_prefetch',
     '__builtin_sub_overflow',
     '__builtin_unreachable',
 ]
-    if cc.has_function(fn)
-        config.set('HAVE_@0@'.format(fn.substring(2).to_upper()), 1)
+    if not cc.has_function(fn)
+        error('@0@ support required'.format(fn))
     endif
 endforeach