diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c05006b8442..f2fdc93c4bd 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2009-04-25  Joseph Myers  <joseph@codesourcery.com>
+
+	PR preprocessor/39559
+	* gcc.dg/c99-intconst-2.c: New test.
+
 2009-04-25  Jan Hubicka  <jh@suse.cz>
 
 	* g++.dg/tree-ssa/ehcleanup-1.C: Update.
diff --git a/gcc/testsuite/gcc.dg/c99-intconst-2.c b/gcc/testsuite/gcc.dg/c99-intconst-2.c
new file mode 100644
index 00000000000..34923675762
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c99-intconst-2.c
@@ -0,0 +1,8 @@
+/* Test for integer constant types: diagnostics for constants outside
+   range of intmax_t must be pedwarns.  PR 39559.  */
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
+
+#if 9223372036854775808LL /* { dg-error "integer constant is so large that it is unsigned" } */
+unsigned long long l = 9223372036854775808LL; /* { dg-error "integer constant is so large that it is unsigned" } */
+#endif
diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index a9ccc59717b..24f3f8debcf 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,9 @@
+2009-04-25  Joseph Myers  <joseph@codesourcery.com>
+
+	PR preprocessor/39559
+	* expr.c (cpp_interpret_integer): Use a pedwarn for decimal
+	constants larger than intmax_t in C99 mode.
+
 2009-04-21  Taras Glek <tglek@mozilla.com>
 
 	* include/cpp-id-data.h: Update GTY annotations to new syntax.
diff --git a/libcpp/expr.c b/libcpp/expr.c
index b9a17db9361..f65fae02431 100644
--- a/libcpp/expr.c
+++ b/libcpp/expr.c
@@ -538,8 +538,27 @@ cpp_interpret_integer (cpp_reader *pfile, const cpp_token *token,
 		    && pfile->state.in_directive)
 	       && !num_positive (result, precision))
 	{
+	  /* This is for constants within the range of uintmax_t but
+	     not that or intmax_t.  For such decimal constants, a
+	     diagnostic is required for C99 as the selected type must
+	     be signed and not having a type is a constraint violation
+	     (DR#298, TC3), so this must be a pedwarn.  For C90,
+	     unsigned long is specified to be used for a constant that
+	     does not fit in signed long; if uintmax_t has the same
+	     range as unsigned long this means only a warning is
+	     appropriate here.  C90 permits the preprocessor to use a
+	     wider range than unsigned long in the compiler, so if
+	     uintmax_t is wider than unsigned long no diagnostic is
+	     required for such constants in preprocessor #if
+	     expressions and the compiler will pedwarn for such
+	     constants outside the range of unsigned long that reach
+	     the compiler so a diagnostic is not required there
+	     either; thus, pedwarn for C99 but use a plain warning for
+	     C90.  */
 	  if (base == 10)
-	    cpp_error (pfile, CPP_DL_WARNING,
+	    cpp_error (pfile, (CPP_OPTION (pfile, c99)
+			       ? CPP_DL_PEDWARN
+			       : CPP_DL_WARNING),
 		       "integer constant is so large that it is unsigned");
 	  result.unsignedp = true;
 	}