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[njs] Ignoring UndefinedBehaviorSanitizer warnings where appropriate.

Dmitry Volyntsev
January 09, 2024 01:18AM
details: https://hg.nginx.org/njs/rev/0490f1ae4cf5
branches:
changeset: 2258:0490f1ae4cf5
user: Dmitry Volyntsev <xeioex@nginx.com>
date: Sun Jul 30 10:21:51 2023 +0100
description:
Ignoring UndefinedBehaviorSanitizer warnings where appropriate.

Prodded by David Carlier and Ben Kallus.

diffstat:

auto/clang | 11 +++++++++++
src/njs_clang.h | 25 +++++++++++++++++++++++++
src/njs_number.c | 4 +++-
src/njs_number.h | 2 +-
src/njs_typed_array.c | 2 +-
5 files changed, 41 insertions(+), 3 deletions(-)

diffs (94 lines):

diff -r 275d785ab5bf -r 0490f1ae4cf5 auto/clang
--- a/auto/clang Mon Jan 08 16:40:42 2024 -0800
+++ b/auto/clang Sun Jul 30 10:21:51 2023 +0100
@@ -161,6 +161,17 @@ njs_feature_test="int main(int argc, cha
. auto/feature


+njs_feature="GCC __attribute__ no_sanitize"
+njs_feature_name=NJS_HAVE_GCC_ATTRIBUTE_NO_SANITIZE
+njs_feature_run=no
+njs_feature_path=
+njs_feature_libs=
+njs_feature_test="__attribute__((no_sanitize(\"undefined\"))) int main(void) {
+ return 0;
+ }"
+. auto/feature
+
+
njs_feature="Address sanitizer"
njs_feature_name=NJS_HAVE_ADDRESS_SANITIZER
njs_feature_run=no
diff -r 275d785ab5bf -r 0490f1ae4cf5 src/njs_clang.h
--- a/src/njs_clang.h Mon Jan 08 16:40:42 2024 -0800
+++ b/src/njs_clang.h Sun Jul 30 10:21:51 2023 +0100
@@ -183,6 +183,31 @@ njs_leading_zeros64(uint64_t x)
#define njs_msan_unpoison(ptr, size)
#endif

+#if (NJS_HAVE_GCC_ATTRIBUTE_NO_SANITIZE)
+#define NJS_NOSANITIZE(options) __attribute__((no_sanitize(options)))
+#else
+#define NJS_NOSANITIZE(options)
+#endif
+
+
+njs_inline NJS_NOSANITIZE("float-cast-overflow") int64_t
+njs_unsafe_cast_double_to_int64(double num)
+{
+ /*
+ * Casting NaN to integer is undefined behavior,
+ * but it is fine in some cases where we do additional checks later.
+ * For example:
+ * int64_t i64 = njs_unsafe_cast_double_to_int64(num);
+ * if (i64 == num) {
+ * // num is integer
+ * }
+ *
+ * We do this as inline function to avoid UndefinedBehaviorSanitizer
+ * warnings.
+ */
+ return (int64_t) num;
+}
+

#if (NJS_HAVE_DENORMALS_CONTROL)
#include <xmmintrin.h>
diff -r 275d785ab5bf -r 0490f1ae4cf5 src/njs_number.c
--- a/src/njs_number.c Mon Jan 08 16:40:42 2024 -0800
+++ b/src/njs_number.c Sun Jul 30 10:21:51 2023 +0100
@@ -382,7 +382,9 @@ njs_number_is_safe_integer(njs_vm_t *vm,
if (nargs > 1 && njs_is_number(&args[1])) {
num = njs_number(&args[1]);

- if (num == (int64_t) num && fabs(num) <= NJS_MAX_SAFE_INTEGER) {
+ if (num == njs_unsafe_cast_double_to_int64(num)
+ && fabs(num) <= NJS_MAX_SAFE_INTEGER)
+ {
integer = 1;
}
}
diff -r 275d785ab5bf -r 0490f1ae4cf5 src/njs_number.h
--- a/src/njs_number.h Mon Jan 08 16:40:42 2024 -0800
+++ b/src/njs_number.h Sun Jul 30 10:21:51 2023 +0100
@@ -36,7 +36,7 @@ njs_int_t njs_number_parse_float(njs_vm_
njs_uint_t nargs, njs_index_t unused, njs_value_t *retval);


-njs_inline njs_bool_t
+njs_inline NJS_NOSANITIZE("float-cast-overflow") njs_bool_t
njs_number_is_integer_index(double num)
{
uint32_t u32;
diff -r 275d785ab5bf -r 0490f1ae4cf5 src/njs_typed_array.c
--- a/src/njs_typed_array.c Mon Jan 08 16:40:42 2024 -0800
+++ b/src/njs_typed_array.c Sun Jul 30 10:21:51 2023 +0100
@@ -1388,7 +1388,7 @@ njs_typed_array_prototype_index_of(njs_v

v = njs_number(njs_argument(args, 1));

- i64 = v;
+ i64 = njs_unsafe_cast_double_to_int64(v);
integer = (v == i64);

buffer = array->buffer;
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Subject Author Views Posted

[njs] Ignoring UndefinedBehaviorSanitizer warnings where appropriate.

Dmitry Volyntsev 239 January 09, 2024 01:18AM

Re: [njs] Ignoring UndefinedBehaviorSanitizer warnings where appropriate.

Ben Kallus 58 January 23, 2024 04:06PM



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