stdio: Fix issue of printing "%La" format with large exp part.

- Currently, printf("%La\n", 1e1000L) crashes with segv due to lack
  of frexpl() function. With this patch, frexpl() function has been
  implemented in libm to solve this issue.

Addresses: https://sourceware.org/pipermail/newlib/2021/018718.html

6 files changed, 87 insertions, 11 deletions

diff --git a/newlib/Makefile.am b/newlib/Makefile.am
index d3da43a4b..1235adb8b 100644
--- a/newlib/Makefile.am
+++ b/newlib/Makefile.am
@@ -105,7 +105,7 @@ MATHOBJS_IN_LIBC = \
 	$(lpfx)s_isnand.$(oext) $(lpfx)sf_isnanf.$(oext) \
 	$(lpfx)s_nan.$(oext) $(lpfx)sf_nan.$(oext) \
 	$(lpfx)s_ldexp.$(oext) $(lpfx)sf_ldexp.$(oext) \
-	$(lpfx)s_frexp.$(oext) $(lpfx)sf_frexp.$(oext) \
+	$(lpfx)s_frexp.$(oext) $(lpfx)sf_frexp.$(oext) $(lpfx)frexpl.$(oext) \
 	$(lpfx)s_modf.$(oext) \
 	$(lpfx)sf_modf.$(oext) $(lpfx)s_scalbn.$(oext) \
 	$(lpfx)sf_scalbn.$(oext) \
diff --git a/newlib/Makefile.in b/newlib/Makefile.in
index bf15dfea3..68417953d 100644
--- a/newlib/Makefile.in
+++ b/newlib/Makefile.in
@@ -312,6 +312,7 @@ pdfdir = @pdfdir@
 prefix = @prefix@
 program_transform_name = @program_transform_name@
 psdir = @psdir@
+runstatedir = @runstatedir@
 sbindir = @sbindir@
 shared_machine_dir = @shared_machine_dir@
 sharedstatedir = @sharedstatedir@
@@ -415,7 +416,7 @@ MATHOBJS_IN_LIBC = \
 	$(lpfx)s_isnand.$(oext) $(lpfx)sf_isnanf.$(oext) \
 	$(lpfx)s_nan.$(oext) $(lpfx)sf_nan.$(oext) \
 	$(lpfx)s_ldexp.$(oext) $(lpfx)sf_ldexp.$(oext) \
-	$(lpfx)s_frexp.$(oext) $(lpfx)sf_frexp.$(oext) \
+	$(lpfx)s_frexp.$(oext) $(lpfx)sf_frexp.$(oext) $(lpfx)frexpl.$(oext) \
 	$(lpfx)s_modf.$(oext) \
 	$(lpfx)sf_modf.$(oext) $(lpfx)s_scalbn.$(oext) \
 	$(lpfx)sf_scalbn.$(oext) \
diff --git a/newlib/libc/include/math.h b/newlib/libc/include/math.h
index 0b6494e6a..799ac494a 100644
--- a/newlib/libc/include/math.h
+++ b/newlib/libc/include/math.h
@@ -509,6 +509,7 @@ extern long double erfcl (long double);
 #else /* !_LDBL_EQ_DBL && !__CYGWIN__ */
 extern long double hypotl (long double, long double);
 extern long double sqrtl (long double);
+extern long double frexpl (long double, int *);
 #ifdef __i386__
 /* Other long double precision functions.  */
 extern _LONG_DOUBLE rintl (_LONG_DOUBLE);
diff --git a/newlib/libc/stdio/vfprintf.c b/newlib/libc/stdio/vfprintf.c
index 1aaf05aa4..c1483c0ac 100644
--- a/newlib/libc/stdio/vfprintf.c
+++ b/newlib/libc/stdio/vfprintf.c
@@ -517,10 +517,7 @@ extern int _ldcheck (_LONG_DOUBLE *);
 
 #  define _PRINTF_FLOAT_TYPE _LONG_DOUBLE
 #  define _DTOA_R _ldtoa_r
-/* FIXME - frexpl is not yet supported; and cvt infloops if (double)f
-   converts a finite value into infinity.  */
-/* #  define FREXP frexpl */
-#  define FREXP(f,e) ((_LONG_DOUBLE) frexp ((double)f, e))
+#  define FREXP frexpl
 # endif /* !_NO_LONGDBL */
 
 static char *cvt(struct _reent *, _PRINTF_FLOAT_TYPE, int, int, char *, int *,
diff --git a/newlib/libc/stdio/vfwprintf.c b/newlib/libc/stdio/vfwprintf.c
index 980b31e3b..7384b37d3 100644
--- a/newlib/libc/stdio/vfwprintf.c
+++ b/newlib/libc/stdio/vfwprintf.c
@@ -243,10 +243,7 @@ extern int _ldcheck (_LONG_DOUBLE *);
 
 #  define _PRINTF_FLOAT_TYPE _LONG_DOUBLE
 #  define _DTOA_R _ldtoa_r
-/* FIXME - frexpl is not yet supported; and cvt infloops if (double)f
-   converts a finite value into infinity.  */
-/* #  define FREXP frexpl */
-#  define FREXP(f,e) ((_LONG_DOUBLE) frexp ((double)f, e))
+#  define FREXP frexpl
 # endif /* !_NO_LONGDBL */
 
 static wchar_t *wcvt(struct _reent *, _PRINTF_FLOAT_TYPE, int, int, wchar_t *,
diff --git a/newlib/libm/common/frexpl.c b/newlib/libm/common/frexpl.c
index 79e41fd9e..22c811689 100644
--- a/newlib/libm/common/frexpl.c
+++ b/newlib/libm/common/frexpl.c
@@ -29,10 +29,11 @@ POSSIBILITY OF SUCH DAMAGE.
 */
 
 #include <math.h>
+#include <float.h>
 #include "local.h"
 
 /* On platforms where long double is as wide as double.  */
-#ifdef _LDBL_EQ_DBL
+#if defined(_LDBL_EQ_DBL) || (LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024)
 long double
 frexpl (long double x, int *eptr)
 {
@@ -40,3 +41,82 @@ frexpl (long double x, int *eptr)
 }
 #endif
 
+#if (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+# if (LDBL_MANT_DIG == 64) /* 80-bit long double */
+union ldbl {
+  long double x;
+  struct {
+#  ifdef __IEEE_LITTLE_ENDIAN /* for Intel CPU */
+    __uint32_t fracl;
+    __uint32_t frach;
+    __uint32_t exp:15;
+    __uint32_t sign:1;
+    __uint32_t pad:16;
+#  endif
+#  ifdef __IEEE_BIG_ENDIAN
+#   ifndef ___IEEE_BYTES_LITTLE_ENDIAN /* for m86k */
+    __uint32_t sign:1;
+    __uint32_t exp:15;
+    __uint32_t pad:16;
+#   else /* ARM FPA10 math copprocessor */
+    __uint32_t exp:15;
+    __uint32_t pad:16;
+    __uint32_t sign:1;
+#   endif
+    __uint32_t frach;
+    __uint32_t fracl;
+#  endif
+  } u32;
+};
+# else /* LDBL_MANT_DIG == 113, 128-bit long double */
+union ldbl {
+  long double x;
+  struct {
+#  ifdef __IEEE_LITTLE_ENDIAN
+    __uint32_t fracl;
+    __uint32_t fraclm;
+    __uint32_t frachm;
+    __uint32_t frach:16;
+    __uint32_t exp:15;
+    __uint32_t sign:1;
+#  endif
+#  ifdef __IEEE_BIG_ENDIAN
+#   ifndef ___IEEE_BYTES_LITTLE_ENDIAN
+    __uint32_t sign:1;
+    __uint32_t exp:15;
+    __uint32_t frach:16;
+#   else /* ARMEL without __VFP_FP__ */
+    __uint32_t frach:16;
+    __uint32_t exp:15;
+    __uint32_t sign:1;
+#   endif
+    __uint32_t frachm;
+    __uint32_t fraclm;
+    __uint32_t fracl;
+#  endif
+  } u32;
+};
+# endif
+
+static const double two114 = 0x1p114;
+
+long double
+frexpl (long double x, int *eptr)
+{
+  union ldbl u;
+  u.x = x;
+  int e = u.u32.exp;
+  *eptr = 0;
+  if (e == 0x7fff || x == 0)
+    return x; /* inf,nan,0 */
+  if (e == 0) /* subnormal */
+    {
+      u.x *= two114;
+      e = u.u32.exp;
+      *eptr -= 114;
+    }
+  *eptr += e - 16382;
+  u.u32.exp = 0x3ffe; /* 0 */
+  return u.x;
+}
+#endif /* End of 80-bit or 128-bit long double */