[lmi-commits] [lmi] master 79298e8c 1/8: Avoid left shift of a negative signed integer in fdlibm

[Greg Chicares]

branch: master
commit 79298e8c443319077f64410d061b82656ed1095a
Author: Gregory W. Chicares <gchicares@sbcglobal.net>
Commit: Gregory W. Chicares <gchicares@sbcglobal.net>

    Avoid left shift of a negative signed integer in fdlibm
    
    * fdlibm_expm1.c: Avoid UB.
    * objects.make: No longer exclude a target that no longer exhibits UB.
    
    See:
      https://lists.nongnu.org/archive/html/lmi/2022-06/msg00061.html
---
 fdlibm_expm1.c | 4 +++-
 objects.make   | 1 -
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fdlibm_expm1.c b/fdlibm_expm1.c
index 5e05e10f..85327355 100644
--- a/fdlibm_expm1.c
+++ b/fdlibm_expm1.c
@@ -239,7 +239,9 @@ double fdlibm_expm1(double x)
         }
         if (k <= -2 || k>56) {     // suffice to return exp(x)-1
             y = one-(e-x);
-            SET_HIGH_WORD(y, hi_uint(y) + (k<<20));    // add k to y's exponent
+            // add k to y's exponent, casting to avoid undefined
+            // behavior (left shift of a negative signed integer)
+            SET_HIGH_WORD(y, hi_uint(y) + (int32_t)(((uint32_t)k)<<20));
             return y-one;
         }
         t = one;
diff --git a/objects.make b/objects.make
index bafd4a0f..ddca37e7 100644
--- a/objects.make
+++ b/objects.make
@@ -360,7 +360,6 @@ ifeq (ubsan,$(build_type))
   excluded_unit_test_targets += \
     actuarial_table_test \
     loads_test \
-    math_functions_test \
     mortality_rates_test \
 
 endif