From 23d76d88630ecee02515e2c8f5c8769cc795ae23 Mon Sep 17 00:00:00 2001

From: Shane Carr <shane@unicode.org>

Date: Fri, 23 Mar 2018 00:56:16 +0000

Subject: [PATCH] ICU-13634 Adding integer overflow logic to ICU4C number

 pipeline in places where it is in ICU4J.

X-SVN-Rev: 41136

diff --git a/icu4c/source/common/putil.cpp b/icu4c/source/common/putil.cpp

index 83f08ac070..452e2fd79c 100644

--- a/icu4c/source/common/putil.cpp

+++ b/icu4c/source/common/putil.cpp

@@ -533,6 +533,30 @@ uprv_fmin(double x, double y)

     return (x > y ? y : x);

 }

+#include <iostream>

+

+U_CAPI UBool U_EXPORT2

+uprv_add32_overflow(int32_t a, int32_t b, int32_t* res) {

+    // NOTE: Some compilers (GCC, Clang) have primitives available, like __builtin_add_overflow.

+    // This function could be optimized by calling one of those primitives.

+    auto a64 = static_cast<int64_t>(a);

+    auto b64 = static_cast<int64_t>(b);

+    int64_t res64 = a64 + b64;

+    *res = static_cast<int32_t>(res64);

+    return res64 != *res;

+}

+

+U_CAPI UBool U_EXPORT2

+uprv_mul32_overflow(int32_t a, int32_t b, int32_t* res) {

+    // NOTE: Some compilers (GCC, Clang) have primitives available, like __builtin_mul_overflow.

+    // This function could be optimized by calling one of those primitives.

+    auto a64 = static_cast<int64_t>(a);

+    auto b64 = static_cast<int64_t>(b);

+    int64_t res64 = a64 * b64;

+    *res = static_cast<int32_t>(res64);

+    return res64 != *res;

+}

+

 /**

  * Truncates the given double.

  * trunc(3.3) = 3.0, trunc (-3.3) = -3.0

diff --git a/icu4c/source/common/putilimp.h b/icu4c/source/common/putilimp.h

index eb9b5380f1..8b858df9e3 100644

--- a/icu4c/source/common/putilimp.h

+++ b/icu4c/source/common/putilimp.h

@@ -391,6 +391,32 @@ U_INTERNAL double  U_EXPORT2 uprv_log(double d);

  */

 U_INTERNAL double  U_EXPORT2 uprv_round(double x);

+/**

+ * Adds the signed integers a and b, storing the result in res.

+ * Checks for signed integer overflow.

+ * Similar to the GCC/Clang extension __builtin_add_overflow

+ *

+ * @param a The first operand.

+ * @param b The second operand.

+ * @param res a + b

+ * @return true if overflow occurred; false if no overflow occurred.

+ * @internal

+ */

+U_INTERNAL UBool U_EXPORT2 uprv_add32_overflow(int32_t a, int32_t b, int32_t* res);

+

+/**

+ * Multiplies the signed integers a and b, storing the result in res.

+ * Checks for signed integer overflow.

+ * Similar to the GCC/Clang extension __builtin_mul_overflow

+ *

+ * @param a The first multiplicand.

+ * @param b The second multiplicand.

+ * @param res a * b

+ * @return true if overflow occurred; false if no overflow occurred.

+ * @internal

+ */

+U_INTERNAL UBool U_EXPORT2 uprv_mul32_overflow(int32_t a, int32_t b, int32_t* res);

+

 #if 0

 /**

  * Returns the number of digits after the decimal point in a double number x.

diff --git a/icu4c/source/test/cintltst/putiltst.c b/icu4c/source/test/cintltst/putiltst.c

index b99d9fca9c..1c3e073041 100644

--- a/icu4c/source/test/cintltst/putiltst.c

+++ b/icu4c/source/test/cintltst/putiltst.c

@@ -128,6 +128,20 @@ static void TestPUtilAPI(void){

         log_err("ERROR: uprv_isInfinite failed.\n");

     }

+    log_verbose("Testing the APIs uprv_add32_overflow and uprv_mul32_overflow\n");

+    int32_t overflow_result;

+    doAssert(FALSE, uprv_add32_overflow(INT32_MAX - 2, 1, &overflow_result), "should not overflow");

+    doAssert(INT32_MAX - 1, overflow_result, "should equal INT32_MAX - 1");

+    doAssert(FALSE, uprv_add32_overflow(INT32_MAX - 2, 2, &overflow_result), "should not overflow");

+    doAssert(INT32_MAX, overflow_result, "should equal exactly INT32_MAX");

+    doAssert(TRUE, uprv_add32_overflow(INT32_MAX - 2, 3, &overflow_result), "should overflow");

+    doAssert(FALSE, uprv_mul32_overflow(INT32_MAX / 5, 4, &overflow_result), "should not overflow");

+    doAssert(INT32_MAX / 5 * 4, overflow_result, "should equal INT32_MAX / 5 * 4");

+    doAssert(TRUE, uprv_mul32_overflow(INT32_MAX / 5, 6, &overflow_result), "should overflow");

+    // Test on negative numbers:

+    doAssert(FALSE, uprv_add32_overflow(-3, -2, &overflow_result), "should not overflow");

+    doAssert(-5, overflow_result, "should equal -5");

+

 #if 0

     log_verbose("Testing the API uprv_digitsAfterDecimal()....\n");

     doAssert(uprv_digitsAfterDecimal(value1), 3, "uprv_digitsAfterDecimal() failed.");

-- 

2.24.1