commit 96a0bf28bfa0f7b46bb17678cf6e3e39fa9a10b1
author Michael Jones <michaelrj@google.com> Wed Nov 10 16:19:29 2021 -0800
committer Copybara-Service <copybara-worker@google.com> Thu Nov 11 10:20:56 2021 -0800
tree 1e7ac4566eb6f2bb65bb4286f2b082aa13447339
parent aa091da5c2e517546a1b6984898c3e8b3cd36db2

[libc] tweak strtof errno behavior

When strtof/d/ld return a subnormal number they may set errno to
ERANGE. This change makes this behavior more consistent by making any
decimal number converting to a subnormal set errno to ERANGE. This
brings it in line with hexadecimals, which currently only set errno to
ERANGE if the number is truncated when converting to a subnormal.

Reviewed By: sivachandra, lntue

Differential Revision: https://reviews.llvm.org/D113626

GitOrigin-RevId: 4cdf9884b60de758243c85a6ac1f94aa975fd10d

src/__support/str_to_float.h

diff --git a/src/__support/str_to_float.h b/src/__support/str_to_float.h
index 90408e7..a768889 100644
--- a/src/__support/str_to_float.h
+++ b/src/__support/str_to_float.h
@@ -308,6 +308,10 @@
     ++exp2;
   }
 
+  if (exp2 == 0) {
+    errno = ERANGE; // NOLINT
+  }
+
   *outputMantissa = finalMantissa;
   *outputExp2 = exp2;
 }

test/src/__support/str_to_float_test.cpp

diff --git a/test/src/__support/str_to_float_test.cpp b/test/src/__support/str_to_float_test.cpp
index 0fbc7c3..0acb40e 100644
--- a/test/src/__support/str_to_float_test.cpp
+++ b/test/src/__support/str_to_float_test.cpp
@@ -206,8 +206,8 @@
 }
 
 TEST_F(LlvmLibcStrToFloatTest, SimpleDecimalConversion64BasicSubnormals) {
-  SimpleDecimalConversionTest<double>("1e-320", 0x7e8, 0);
-  SimpleDecimalConversionTest<double>("1e-308", 0x730d67819e8d2, 0);
+  SimpleDecimalConversionTest<double>("1e-320", 0x7e8, 0, ERANGE);
+  SimpleDecimalConversionTest<double>("1e-308", 0x730d67819e8d2, 0, ERANGE);
   SimpleDecimalConversionTest<double>("2.9e-308", 0x14da6df5e4bcc8, 1);
 }
 
@@ -217,7 +217,7 @@
   // but this is the shortest string that results in the maximum subnormal that
   // I found.
   SimpleDecimalConversionTest<double>("2.225073858507201e-308", 0xfffffffffffff,
-                                      0);
+                                      0, ERANGE);
 
   // Same here, if you were to extend the max subnormal out for another 800
   // digits, incrementing any one of those digits would create a normal number.
@@ -227,7 +227,8 @@
 
 TEST_F(LlvmLibcStrToFloatTest, SimpleDecimalConversion32SpecificFailures) {
   SimpleDecimalConversionTest<float>(
-      "1.4012984643248170709237295832899161312802619418765e-45", 0x1, 0);
+      "1.4012984643248170709237295832899161312802619418765e-45", 0x1, 0,
+      ERANGE);
 }
 
 TEST(LlvmLibcStrToFloatTest, SimpleDecimalConversionExtraTypes) {

test/src/stdlib/strtof_test.cpp

diff --git a/test/src/stdlib/strtof_test.cpp b/test/src/stdlib/strtof_test.cpp
index 2109e7d..664133c 100644
--- a/test/src/stdlib/strtof_test.cpp
+++ b/test/src/stdlib/strtof_test.cpp
@@ -82,7 +82,8 @@
 }
 
 TEST_F(LlvmLibcStrToFTest, DecimalSubnormals) {
-  runTest("1.4012984643248170709237295832899161312802619418765e-45", 55, 0x1);
+  runTest("1.4012984643248170709237295832899161312802619418765e-45", 55, 0x1,
+          ERANGE);
 }
 
 TEST_F(LlvmLibcStrToFTest, DecimalWithLongExponent) {