APItest: get a compile-time warning if IVdf doesn't match IV_MAX

and similarly for UVuf/UV_MAX.

This already warns in PPPort, but that's for testing PPPort, not
the core.

2 files changed, 24 insertions, 1 deletions

diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index bc4805127a..3cf8eeff86 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -4505,6 +4505,17 @@ PerlIO_stdin()
 FILE *
 PerlIO_exportFILE(PerlIO *f, const char *mode)
 
+SV *
+test_MAX_types()
+    CODE:
+        /* tests that IV_MAX and UV_MAX have types suitable
+           for the IVdf and UVdf formats.
+           If this warns then don't add casts here.
+        */
+        RETVAL = newSVpvf("iv %" IVdf " uv %" UVuf, IV_MAX, UV_MAX);
+    OUTPUT:
+	RETVAL
+
 MODULE = XS::APItest PACKAGE = XS::APItest::AUTOLOADtest
 
 int
diff --git a/ext/XS-APItest/t/printf.t b/ext/XS-APItest/t/printf.t
index 968fdc4627..28f21e35e1 100644
--- a/ext/XS-APItest/t/printf.t
+++ b/ext/XS-APItest/t/printf.t
@@ -6,7 +6,7 @@ BEGIN {
   }
 }
 
-use Test::More tests => 11;
+use Test::More tests => 12;
 
 BEGIN { use_ok('XS::APItest') };
 
@@ -51,3 +51,15 @@ SKIP: {
    is($output[4], "7.000", "print_long_double");
 }
 
+{
+    # GH #17338
+    # This is unlikely to fail here since int and long are the
+    # same size on our usual platforms, but it's less likely to
+    # be ignored than the warning that's the real diagnostic
+    # for this bug.
+    my $uv_max = ~0;
+    my $iv_max = $uv_max >> 1;
+    my $max_out = "iv $iv_max uv $uv_max";
+    is(test_MAX_types(), $max_out,
+       "check types for IV_MAX and UV_MAX match IVdf/UVuf");
+}