[libc] Add inf/nan tests for strfrom*() functions

[vinayakdsci]

Adds tests for inf and nan values to the tests for strfrom*() functions.

Also marks some variables as [[maybe_unused]] to silence unused variable warnings.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Vinayak Dev (vinayakdsci)

Changes

Adds tests for inf and nan values to the tests for strfrom*() functions.

Also marks some variables as [[maybe_unused]] to silence unused variable warnings.

---

Full diff: https://github.com/llvm/llvm-project/pull/86663.diff

2 Files Affected:

• (modified) libc/test/src/stdlib/CMakeLists.txt (+1)
• (modified) libc/test/src/stdlib/StrfromTest.h (+81-10)

diff --git a/libc/test/src/stdlib/CMakeLists.txt b/libc/test/src/stdlib/CMakeLists.txt
index 3ccc1cde91934c..28c5b566cc4772 100644
--- a/libc/test/src/stdlib/CMakeLists.txt
+++ b/libc/test/src/stdlib/CMakeLists.txt
@@ -174,6 +174,7 @@ add_header_library(
   StrfromTest.h
   DEPENDS
   libc.src.__support.CPP.type_traits
+  libc.src.__support.FPUtil.fp_bits
 )
 
 add_libc_test(
diff --git a/libc/test/src/stdlib/StrfromTest.h b/libc/test/src/stdlib/StrfromTest.h
index f695bbb335bdbe..0b9a48e69165c1 100644
--- a/libc/test/src/stdlib/StrfromTest.h
+++ b/libc/test/src/stdlib/StrfromTest.h
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/FPUtil/FPBits.h"
 #include "test/UnitTest/Test.h"
 
 #define ASSERT_STREQ_LEN(actual_written, actual_str, expected_str)             \
@@ -68,11 +69,27 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
     written = func(buff, 37, "A simple string with no conversions.", 1.0);
     ASSERT_STREQ_LEN(written, buff, "A simple string with no conversions.");
 
-    written =
-        func(buff, 37,
-             "%A simple string with one conversion, should overwrite.", 1.0);
-    ASSERT_STREQ_LEN(written, buff, is_long_double ? "0X8P-3" : "0X1P+0");
-
+    if (is_long_double) {
+      // 64-bit long double values require checking as they will give
+      // a different result
+#if defined(LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64)
+      written =
+          func(buff, 37,
+               "%A simple string with one conversion, should overwrite.", 1.0);
+      ASSERT_STREQ_LEN(written, buff, "0X1P+0");
+#else
+      written =
+          func(buff, 37,
+               "%A simple string with one conversion, should overwrite.", 1.0);
+      ASSERT_STREQ_LEN(written, buff, "0X8P-3");
+#endif
+    } else {
+      // not long double
+      written =
+          func(buff, 37,
+               "%A simple string with one conversion, should overwrite.", 1.0);
+      ASSERT_STREQ_LEN(written, buff, "0X1P+0");
+    }
     written = func(buff, 74,
                    "A simple string with one conversion in %A "
                    "between, writes string as it is",
@@ -105,6 +122,13 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
     ASSERT_STREQ(buff, "1.05"); // Make sure that buff has not changed
   }
 
+  void infNanValues(FunctionT func) {
+    if(is_double_prec)
+      doublePrecInfNan(func);
+    else if(!is_single_prec)
+      longDoublePrecInfNan(func);
+  }
+
   void floatDecimalSinglePrec(FunctionT func) {
     char buff[70];
     int written;
@@ -336,8 +360,10 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
   }
 
   void floatDecimalExpLongDoublePrec(FunctionT func) {
-    char buff[100];
-    int written;
+    // Mark as maybe_unused to silence unused variable
+    // warning when long double is not 80-bit
+    [[maybe_unused]] char buff[100];
+    [[maybe_unused]] int written;
 
 #if defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
     written = func(buff, 90, "%.9e", 1000000000500000000.1L);
@@ -399,8 +425,10 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
   }
 
   void floatDecimalAutoLongDoublePrec(FunctionT func) {
-    char buff[100];
-    int written;
+    // Mark as maybe_unused to silence unused variable
+    // warning when long double is not 80-bit
+    [[maybe_unused]] char buff[100];
+    [[maybe_unused]] int written;
 
 #if defined(LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80)
     written = func(buff, 99, "%g", 0xf.fffffffffffffffp+16380L);
@@ -413,6 +441,48 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
     ASSERT_STREQ_LEN(written, buff, "1e-99");
 #endif // LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
   }
+
+  void doublePrecInfNan(FunctionT func) {
+    char buff[15];
+    int written;
+
+    double inf = LIBC_NAMESPACE::fputil::FPBits<double>::inf().get_val();
+    double nan = LIBC_NAMESPACE::fputil::FPBits<double>::quiet_nan().get_val();
+
+    written = func(buff, 10, "%f", inf);
+    ASSERT_STREQ_LEN(written, buff, "inf");
+
+    written = func(buff, 10, "%A", -inf);
+    ASSERT_STREQ_LEN(written, buff, "-INF");
+
+    written = func(buff, 10, "%f", nan);
+    ASSERT_STREQ_LEN(written, buff, "nan");
+
+    written = func(buff, 10, "%A", -nan);
+    ASSERT_STREQ_LEN(written, buff, "-NAN");
+  }
+
+  void longDoublePrecInfNan(FunctionT func) {
+    char buff[15];
+    int written;
+
+    long double ld_inf =
+        LIBC_NAMESPACE::fputil::FPBits<long double>::inf().get_val();
+    long double ld_nan =
+        LIBC_NAMESPACE::fputil::FPBits<long double>::quiet_nan().get_val();
+
+    written = func(buff, 10, "%f", ld_inf);
+    ASSERT_STREQ_LEN(written, buff, "inf");
+
+    written = func(buff, 10, "%A", -ld_inf);
+    ASSERT_STREQ_LEN(written, buff, "-INF");
+
+    written = func(buff, 10, "%f", ld_nan);
+    ASSERT_STREQ_LEN(written, buff, "nan");
+
+    written = func(buff, 10, "%A", -ld_nan);
+    ASSERT_STREQ_LEN(written, buff, "-NAN");
+  }
 };
 
 #define STRFROM_TEST(InputType, name, func)                                    \
@@ -432,4 +502,5 @@ class StrfromTest : public LIBC_NAMESPACE::testing::Test {
   }                                                                            \
   TEST_F(LlvmLibc##name##Test, InsufficientBufferSize) {                       \
     insufficentBufsize(func);                                                  \
-  }
+  }                                                                            \
+  TEST_F(LlvmLibc##name##Test, InfAndNanValues) { infNanValues(func); }

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[michaelrj-google]

This patch LGTM

If you're looking for more things to do, then adding the strfrom functions to the bazel build would also be useful.

[vinayakdsci]

This patch LGTM

Thanks! Could you land this for me?

If you're looking for more things to do, then adding the strfrom functions to the bazel build would also be useful.

OK, I will look into that too. It might take some time, though, as I would need to familiarise myself with bazel.

[gchatelet]

long double can be 64, 80 or 128 bits so technically we'd need the following cases:

• LIBC_TYPES_LONG_DOUBLE_IS_FLOAT64
• LIBC_TYPES_LONG_DOUBLE_IS_X86_FLOAT80
• LIBC_TYPES_LONG_DOUBLE_IS_FLOAT128

[vinayakdsci]

@gchatelet The tests work for 64 bit and 80-bit long doubles, but I am unsure on how to test for 128 bit ones. Do you have any pointers?

[vinayakdsci]

@gchatelet I am sorry, I ran some tests on my computer using libquadmath, and I found that 64-bit and 128-bit floats give identical outputs, while 80-bits do not. I will update the tests, and re-push.
Thanks for the review!