From db42c87936a1111024c002dbc64cc9e2a4613a54 Mon Sep 17 00:00:00 2001
From: Fredrik Roubert <roubert@google.com>
Date: Thu, 21 Nov 2024 18:40:15 +0100
Subject: [PATCH] ICU-22954 A build test for C++ header-only APIs with C++ APIs
 disabled.

---
 icu4c/source/test/intltest/Makefile.in                |  2 +-
 .../test/intltest/cplusplus_header_api_build_test.cpp | 11 +++++++++++
 icu4c/source/test/intltest/intltest.vcxproj           |  1 +
 icu4c/source/test/intltest/intltest.vcxproj.filters   |  3 +++
 4 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 icu4c/source/test/intltest/cplusplus_header_api_build_test.cpp

diff --git a/icu4c/source/test/intltest/Makefile.in b/icu4c/source/test/intltest/Makefile.in
index b9a78e634e4..5d4a03bc678 100644
--- a/icu4c/source/test/intltest/Makefile.in
+++ b/icu4c/source/test/intltest/Makefile.in
@@ -75,7 +75,7 @@ numbertest_parse.o numbertest_doubleconversion.o numbertest_skeletons.o \
 static_unisets_test.o numfmtdatadriventest.o numbertest_range.o erarulestest.o \
 formattedvaluetest.o formatted_string_builder_test.o numbertest_permutation.o \
 units_data_test.o units_router_test.o units_test.o displayoptions_test.o \
-numbertest_simple.o uchar_type_build_test.o ucolheaderonlytest.o usetheaderonlytest.o
+numbertest_simple.o cplusplus_header_api_build_test.o uchar_type_build_test.o ucolheaderonlytest.o usetheaderonlytest.o
 
 DEPS = $(OBJECTS:.o=.d)
 
diff --git a/icu4c/source/test/intltest/cplusplus_header_api_build_test.cpp b/icu4c/source/test/intltest/cplusplus_header_api_build_test.cpp
new file mode 100644
index 00000000000..d3381999484
--- /dev/null
+++ b/icu4c/source/test/intltest/cplusplus_header_api_build_test.cpp
@@ -0,0 +1,11 @@
+// © 2025 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html#License
+
+// ICU-22954 Test that client code can be built with U_SHOW_CPLUSPLUS_API=0.
+#undef U_ALL_IMPLEMENTATION
+#undef U_SHOW_CPLUSPLUS_API
+#define U_SHOW_CPLUSPLUS_API 0
+#include "unicode/char16ptr.h"
+#include "unicode/ucol.h"
+#include "unicode/uset.h"
+#include "unicode/utypes.h"
diff --git a/icu4c/source/test/intltest/intltest.vcxproj b/icu4c/source/test/intltest/intltest.vcxproj
index c561e95bc76..7c0b089a36e 100644
--- a/icu4c/source/test/intltest/intltest.vcxproj
+++ b/icu4c/source/test/intltest/intltest.vcxproj
@@ -241,6 +241,7 @@
     <ClCompile Include="units_data_test.cpp" />
     <ClCompile Include="units_router_test.cpp" />
     <ClCompile Include="units_test.cpp" />
+    <ClCompile Include="cplusplus_header_api_build_test.cpp" />
     <ClCompile Include="uchar_type_build_test.cpp" />
     <ClCompile Include="ucolheaderonlytest.cpp" />
     <ClCompile Include="usetheaderonlytest.cpp" />
diff --git a/icu4c/source/test/intltest/intltest.vcxproj.filters b/icu4c/source/test/intltest/intltest.vcxproj.filters
index 61acf3beb30..cea62b786d2 100644
--- a/icu4c/source/test/intltest/intltest.vcxproj.filters
+++ b/icu4c/source/test/intltest/intltest.vcxproj.filters
@@ -568,6 +568,9 @@
     <ClCompile Include="units_test.cpp">
       <Filter>formatting</Filter>
     </ClCompile>
+    <ClCompile Include="cplusplus_header_api_build_test.cpp">
+      <Filter>configuration</Filter>
+    </ClCompile>
     <ClCompile Include="uchar_type_build_test.cpp">
       <Filter>configuration</Filter>
     </ClCompile>