2021-05-18  Joern Rennecke  <joern.rennecke@riscy-ip.com>

    libstdc++: Disable floating_to_chars.cc on 16 bit targets
    
    This patch conditionally disables the compilation of floating_to_chars.cc
    on 16 bit targets, thus fixing a build failure for these targets as
    the POW10_SPLIT_2 array exceeds the maximum object size.

libstdc++-v3/
	PR libstdc++/100361
	* include/std/charconv (to_chars): Hide the overloads for
	floating-point types for 16 bit targets.
	* src/c++17/floating_to_chars.cc: Don't compile for 16 bit targets.
	* testsuite/20_util/to_chars/double.cc: Run this test only on
	size32plus targets.
	* testsuite/20_util/to_chars/float.cc: Likewise.
	* testsuite/20_util/to_chars/long_double.cc: Likewise.

diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
index 193702e677a..ac9c34d4601 100644
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -703,7 +703,8 @@ namespace __detail
 	     chars_format __fmt = chars_format::general) noexcept;
 #endif
 
-#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
+#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 \
+    && __SIZE_WIDTH__ >= 32
   // Floating-point std::to_chars
 
   // Overloads for float.
diff --git a/libstdc++-v3/src/c++17/floating_to_chars.cc b/libstdc++-v3/src/c++17/floating_to_chars.cc
index 1a0abb9e80f..44f547a77b4 100644
--- a/libstdc++-v3/src/c++17/floating_to_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_to_chars.cc
@@ -50,7 +50,9 @@ extern "C" int __sprintfieee128(char*, const char*, ...);
 
 // This implementation crucially assumes float/double have the
 // IEEE binary32/binary64 formats.
-#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
+#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 \
+    /* And it also assumes that uint64_t POW10_SPLIT_2[3133][3] is valid.  */\
+    && __SIZE_WIDTH__ >= 32
 
 // Determine the binary format of 'long double'.
 
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/double.cc b/libstdc++-v3/testsuite/20_util/to_chars/double.cc
index bb6f74424ed..64e62213044 100644
--- a/libstdc++-v3/testsuite/20_util/to_chars/double.cc
+++ b/libstdc++-v3/testsuite/20_util/to_chars/double.cc
@@ -33,6 +33,7 @@
 
 // { dg-do run { target c++17 } }
 // { dg-require-effective-target ieee-floats }
+// { dg-require-effective-target size32plus }
 
 #include <charconv>
 
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/float.cc b/libstdc++-v3/testsuite/20_util/to_chars/float.cc
index 0c8dd4f66df..73b9081d4ff 100644
--- a/libstdc++-v3/testsuite/20_util/to_chars/float.cc
+++ b/libstdc++-v3/testsuite/20_util/to_chars/float.cc
@@ -33,6 +33,7 @@
 
 // { dg-do run { target c++17 } }
 // { dg-require-effective-target ieee-floats }
+// { dg-require-effective-target size32plus }
 
 #include <charconv>
 
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc b/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc
index 8cf45ad5e94..447e5368811 100644
--- a/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc
+++ b/libstdc++-v3/testsuite/20_util/to_chars/long_double.cc
@@ -35,6 +35,7 @@
 // { dg-xfail-run-if "Non-conforming printf (see PR98384)" { *-*-solaris* *-*-darwin* } }
 
 // { dg-require-effective-target ieee-floats }
+// { dg-require-effective-target size32plus }
 
 #include <charconv>