Stop raising OverflowError on underflows reported by libm (errno==ERANGE and
libm result is 0). Cautiously add a few libm exception test cases:
1. That exp(-huge) returns 0 without exception.
2. That exp(+huge) triggers OverflowError.
3. That sqrt(-1) raises ValueError specifically (apparently under glibc linked
with -lieee, it was raising OverflowError due to an accident of the way
mathmodule.c's CHECK() macro happened to deal with Infs and NaNs under gcc).
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 6d6bc44..1f31dc5 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -152,3 +152,32 @@
print 'tanh'
testit('tanh(0)', math.tanh(0), 0)
testit('tanh(1)+tanh(-1)', math.tanh(1)+math.tanh(-1), 0)
+
+print 'exceptions' # oooooh, *this* is a x-platform gamble! good luck
+
+try:
+ x = math.exp(-1000000000)
+except:
+ # mathmodule.c is failing to weed out underflows from libm, or
+ # we've got an fp format with huge dynamic range
+ raise TestFailed("underflowing exp() should not have rasied an exception")
+if x != 0:
+ raise TestFailed("underflowing exp() should have returned 0")
+
+# If this fails, probably using a strict IEEE-754 conforming libm, and x
+# is +Inf afterwards. But Python wants overflows detected by default.
+try:
+ x = math.exp(1000000000)
+except OverflowError:
+ pass
+else:
+ raise TestFailed("overflowing exp() didn't trigger OverflowError")
+
+# If this fails, it could be a puzzle. One odd possibility is that
+# mathmodule.c's CHECK() macro is getting confused while comparing
+# Inf (HUGE_VAL) to a NaN, and artificially setting errno to ERANGE
+# as a result (and so raising OverflowError instead).
+try:
+ x = math.sqrt(-1.0)
+except ValueError:
+ pass