[libcxx-commits] [libcxx] [libcxxabi] [libcxx] [test] Detect the UCRT printf("%a") formatting bug (PR #99846)

[Martin Storsjö via libcxx-commits]

https://github.com/mstorsjo updated https://github.com/llvm/llvm-project/pull/99846

>From a0babe3fedfdcf72db34bedb955a3bb406b28015 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Fri, 12 Aug 2022 00:28:01 +0300
Subject: [PATCH] [libcxx] [test] Detect the UCRT printf("%a") formatting bug

This fixes testing with MinGW, if built without __USE_MINGW_ANSI_STDIO=1.

On x86 MinGW, such a configuration fails printf tests with long
doubles due to mismatches between 80 and 64 bit long doubles - but on
ARM, there's no such issue, so building without __USE_MINGW_ANSI_STDIO=1
is perfectly valid there.

Add another similar XFAIL to a libcxxabi test; this test isn't
executed in MSVC environments, so no XFAIL has been needed so far.
---
 .../put_double.hex.pass.cpp                   |  5 +----
 .../put_long_double.hex.pass.cpp              |  5 +----
 libcxx/utils/libcxx/test/features.py          | 20 +++++++++++++++++++
 libcxxabi/test/test_demangle.pass.cpp         |  2 ++
 4 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_double.hex.pass.cpp b/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_double.hex.pass.cpp
index 21efa978abdcc..946c26398fcb8 100644
--- a/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_double.hex.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_double.hex.pass.cpp
@@ -12,10 +12,7 @@
 
 // iter_type put(iter_type s, ios_base& iob, char_type fill, double v) const;
 
-// With the Microsoft UCRT, printf("%a", 0.0) produces "0x0.0000000000000p+0"
-// while other C runtimes produce just "0x0p+0".
-// https://developercommunity.visualstudio.com/t/Printf-formatting-of-float-as-hex-prints/1660844
-// XFAIL: msvc
+// XFAIL: win32-broken-printf-a-precision
 
 // XFAIL: LIBCXX-AIX-FIXME
 
diff --git a/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.hex.pass.cpp b/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.hex.pass.cpp
index c97c9a0c40369..a195c34e5f8e8 100644
--- a/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.hex.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.hex.pass.cpp
@@ -12,10 +12,7 @@
 
 // iter_type put(iter_type s, ios_base& iob, char_type fill, long double v) const;
 
-// With the Microsoft UCRT, printf("%a", 0.0) produces "0x0.0000000000000p+0"
-// while other C runtimes produce just "0x0p+0".
-// https://developercommunity.visualstudio.com/t/Printf-formatting-of-float-as-hex-prints/1660844
-// XFAIL: msvc
+// XFAIL: win32-broken-printf-a-precision
 
 // XFAIL: LIBCXX-AIX-FIXME
 
diff --git a/libcxx/utils/libcxx/test/features.py b/libcxx/utils/libcxx/test/features.py
index 5e708da4f8fbe..fece22d1cdfd8 100644
--- a/libcxx/utils/libcxx/test/features.py
+++ b/libcxx/utils/libcxx/test/features.py
@@ -263,6 +263,26 @@ def _mingwSupportsModules(cfg):
           """,
         ),
     ),
+    # Check for a Windows UCRT bug (not fixed upstream yet).
+    # With UCRT, printf("%a", 0.0) produces "0x0.0000000000000p+0",
+    # while other C runtimes produce just "0x0p+0".
+    # https://developercommunity.visualstudio.com/t/Printf-formatting-of-float-as-hex-prints/1660844
+    Feature(
+        name="win32-broken-printf-a-precision",
+        when=lambda cfg: "_WIN32" in compilerMacros(cfg)
+        and not programSucceeds(
+            cfg,
+            """
+            #include <stdio.h>
+            #include <string.h>
+            int main(int, char**) {
+              char buf[100];
+              snprintf(buf, sizeof(buf), "%a", 0.0);
+              return strcmp(buf, "0x0p+0");
+            }
+          """,
+        ),
+    ),
     # Check for Glibc < 2.27, where the ru_RU.UTF-8 locale had
     # mon_decimal_point == ".", which our tests don't handle.
     Feature(
diff --git a/libcxxabi/test/test_demangle.pass.cpp b/libcxxabi/test/test_demangle.pass.cpp
index fe5598991b831..ab783cf9d96f2 100644
--- a/libcxxabi/test/test_demangle.pass.cpp
+++ b/libcxxabi/test/test_demangle.pass.cpp
@@ -17,6 +17,8 @@
 // 80-bit format, and this demangling test is failing on it.
 // XFAIL: LIBCXX-ANDROID-FIXME && target={{i686|x86_64}}-{{.+}}-android{{.*}}
 
+// XFAIL: win32-broken-printf-a-precision
+
 #include "support/timer.h"
 #include <algorithm>
 #include <cassert>