[libcxx-commits] [libcxx] [libc++] [test] Fix MSVC warnings (PR #93257)

Thu May 23 17:10:30 PDT 2024

llvmbot wrote:




@llvm/pr-subscribers-libcxx

Author: Stephan T. Lavavej (StephanTLavavej)

<details>
<summary>Changes</summary>

Found while running libc++'s tests with MSVC's STL.

* Avoid MSVC warning C5101: use of preprocessor directive in function-like macro argument list is undefined behavior.
  + We can easily make this portable by extracting `constexpr bool is_newlib`.
  + Followup to #73440.
  + See #73598.
  + See #73836.
* Avoid MSVC warning C4267: 'return': conversion from 'size_t' to 'int', possible loss of data.
  + This warning is valid, but harmless for the test, so `static_cast<int>` will avoid it.
* Avoid MSVC warning C4146: unary minus operator applied to unsigned type, result still unsigned.
  + This warning is also valid (the scenario is sometimes intentional, but surprising enough that it's worth warning about). This is a C++17 test, so we can easily avoid it by testing `is_signed_v` at compile-time before testing `m < 0` and `n < 0` at run-time.
* Silence MSVC warning C4310: cast truncates constant value.
  + These warnings are being emitted by `T(255)`. Disabling the warning is simpler than attempting to restructure the code.
  + Followup to #79791.
* MSVC no longer emits warning C4521: multiple copy constructors specified.
  + This warning was removed from the compiler, since at least 2021-12-09.


---
Full diff: https://github.com/llvm/llvm-project/pull/93257.diff


8 Files Affected:

- (modified) libcxx/test/std/atomics/atomics.ref/compare_exchange_strong.pass.cpp (+3) 
- (modified) libcxx/test/std/atomics/atomics.ref/compare_exchange_weak.pass.cpp (+3) 
- (modified) libcxx/test/std/atomics/atomics.ref/wait.pass.cpp (+3) 
- (modified) libcxx/test/std/containers/views/views.span/span.cons/initializer_list.pass.cpp (+2-2) 
- (modified) libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp (+6-3) 
- (modified) libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp (+6-3) 
- (modified) libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp (+6-4) 
- (modified) libcxx/test/support/msvc_stdlib_force_include.h (-1) 


``````````diff

diff --git a/libcxx/test/std/atomics/atomics.ref/compare_exchange_strong.pass.cpp b/libcxx/test/std/atomics/atomics.ref/compare_exchange_strong.pass.cpp
index 72b2f444c476c..90aa5ea5b6df4 100644
--- a/libcxx/test/std/atomics/atomics.ref/compare_exchange_strong.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.ref/compare_exchange_strong.pass.cpp
@@ -9,6 +9,9 @@
 // XFAIL: !has-64-bit-atomics
 // XFAIL: !has-1024-bit-atomics
 
+// MSVC warning C4310: cast truncates constant value
+// ADDITIONAL_COMPILE_FLAGS(cl-style-warnings): /wd4310
+
 // bool compare_exchange_strong(T&, T, memory_order, memory_order) const noexcept;
 // bool compare_exchange_strong(T&, T, memory_order = memory_order::seq_cst) const noexcept;
 
diff --git a/libcxx/test/std/atomics/atomics.ref/compare_exchange_weak.pass.cpp b/libcxx/test/std/atomics/atomics.ref/compare_exchange_weak.pass.cpp
index 5219a8e3714f9..99c1385a2fe0b 100644
--- a/libcxx/test/std/atomics/atomics.ref/compare_exchange_weak.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.ref/compare_exchange_weak.pass.cpp
@@ -9,6 +9,9 @@
 // XFAIL: !has-64-bit-atomics
 // XFAIL: !has-1024-bit-atomics
 
+// MSVC warning C4310: cast truncates constant value
+// ADDITIONAL_COMPILE_FLAGS(cl-style-warnings): /wd4310
+
 // bool compare_exchange_weak(T&, T, memory_order, memory_order) const noexcept;
 // bool compare_exchange_weak(T&, T, memory_order = memory_order::seq_cst) const noexcept;
 
diff --git a/libcxx/test/std/atomics/atomics.ref/wait.pass.cpp b/libcxx/test/std/atomics/atomics.ref/wait.pass.cpp
index e5310febf5c5e..f246803ba2592 100644
--- a/libcxx/test/std/atomics/atomics.ref/wait.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.ref/wait.pass.cpp
@@ -11,6 +11,9 @@
 // XFAIL: !has-64-bit-atomics
 // XFAIL: !has-1024-bit-atomics
 
+// MSVC warning C4310: cast truncates constant value
+// ADDITIONAL_COMPILE_FLAGS(cl-style-warnings): /wd4310
+
 // void wait(T, memory_order = memory_order::seq_cst) const noexcept;
 
 #include <atomic>
diff --git a/libcxx/test/std/containers/views/views.span/span.cons/initializer_list.pass.cpp b/libcxx/test/std/containers/views/views.span/span.cons/initializer_list.pass.cpp
index 74a5094f61261..bc76e23fea3c0 100644
--- a/libcxx/test/std/containers/views/views.span/span.cons/initializer_list.pass.cpp
+++ b/libcxx/test/std/containers/views/views.span/span.cons/initializer_list.pass.cpp
@@ -93,9 +93,9 @@ constexpr bool test() {
 
 // Test P2447R4 "Annex C examples"
 
-constexpr int three(std::span<void* const> sp) { return sp.size(); }
+constexpr int three(std::span<void* const> sp) { return static_cast<int>(sp.size()); }
 
-constexpr int four(std::span<const std::any> sp) { return sp.size(); }
+constexpr int four(std::span<const std::any> sp) { return static_cast<int>(sp.size()); }
 
 bool test_P2447R4_annex_c_examples() {
   // 1. Overload resolution is affected
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp
index d4bbde75ae882..f9e49d02b8860 100644
--- a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/generic_category.pass.cpp
@@ -50,12 +50,15 @@ int main(int, char**)
         // responds with an empty message, which we probably want to
         // treat as a failure code otherwise, but we can detect that
         // with the preprocessor.
+#if defined(_NEWLIB_VERSION)
+        [[maybe_unused]] constexpr bool is_newlib = true;
+#else
+        [[maybe_unused]] constexpr bool is_newlib = false;
+#endif
         LIBCPP_ASSERT(msg.rfind("Error -1 occurred", 0) == 0       // AIX
                       || msg.rfind("No error information", 0) == 0 // Musl
                       || msg.rfind("Unknown error", 0) == 0        // Glibc
-#if defined(_NEWLIB_VERSION)
-                      || msg.empty()
-#endif
+                      || (is_newlib && msg.empty())
         );
         assert(errno == E2BIG);
     }
diff --git a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
index eefbddd27a7f5..a14d6cd6cb4fb 100644
--- a/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
+++ b/libcxx/test/std/diagnostics/syserr/syserr.errcat/syserr.errcat.objects/system_category.pass.cpp
@@ -56,12 +56,15 @@ int main(int, char**) {
     // responds with an empty message, which we probably want to
     // treat as a failure code otherwise, but we can detect that
     // with the preprocessor.
+#if defined(_NEWLIB_VERSION)
+    [[maybe_unused]] constexpr bool is_newlib = true;
+#else
+    [[maybe_unused]] constexpr bool is_newlib = false;
+#endif
     LIBCPP_ASSERT(msg.rfind("Error -1 occurred", 0) == 0       // AIX
                   || msg.rfind("No error information", 0) == 0 // Musl
                   || msg.rfind("Unknown error", 0) == 0        // Glibc
-#if defined(_NEWLIB_VERSION)
-                  || msg.empty()
-#endif
+                  || (is_newlib && msg.empty())
     );
     assert(errno == E2BIG);
   }
diff --git a/libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp b/libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
index 212804356a056..bf40b174b209c 100644
--- a/libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
+++ b/libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
@@ -57,10 +57,12 @@ T basic_gcd_(T m, T n) {
 template <typename T>
 T basic_gcd(T m, T n) {
   using Tp = std::make_unsigned_t<T>;
-  if (m < 0 && m != std::numeric_limits<T>::min())
-    m = -m;
-  if (n < 0 && n != std::numeric_limits<T>::min())
-    n = -n;
+  if constexpr (std::is_signed_v<T>) {
+    if (m < 0 && m != std::numeric_limits<T>::min())
+      m = -m;
+    if (n < 0 && n != std::numeric_limits<T>::min())
+      n = -n;
+  }
   return basic_gcd_(static_cast<Tp>(m), static_cast<Tp>(n));
 }
 
diff --git a/libcxx/test/support/msvc_stdlib_force_include.h b/libcxx/test/support/msvc_stdlib_force_include.h
index 6c26085e72c45..35783c1607b0e 100644
--- a/libcxx/test/support/msvc_stdlib_force_include.h
+++ b/libcxx/test/support/msvc_stdlib_force_include.h
@@ -67,7 +67,6 @@ const AssertionDialogAvoider assertion_dialog_avoider{};
 // Silence compiler warnings.
 #  pragma warning(disable : 4180)  // qualifier applied to function type has no meaning; ignored
 #  pragma warning(disable : 4324)  // structure was padded due to alignment specifier
-#  pragma warning(disable : 4521)  // multiple copy constructors specified
 #  pragma warning(disable : 4702)  // unreachable code
 #  pragma warning(disable : 28251) // Inconsistent annotation for 'new': this instance has no annotations.
 #endif                             // !defined(__clang__)

``````````

</details>


https://github.com/llvm/llvm-project/pull/93257
