Warn on BP5+Blosc in ADIOS2 v2.9 up to patch level 1

include/openPMD/IO/ADIOS/ADIOS2IOHandler.hpp

@@ -440,6 +440,12 @@ class ADIOS2IOHandlerImpl
         Extent const &extent,
         adios2::IO &IO,
         std::string const &var);
+
+    struct
+    {
+        bool noGroupBased = false;
+        bool blosc2bp5 = false;
+    } printedWarningsAlready;
 }; // ADIOS2IOHandlerImpl
 
 /*

src/IO/ADIOS/ADIOS2IOHandler.cpp

@@ -645,6 +645,42 @@ void ADIOS2IOHandlerImpl::createDataset(
             parameters.extent.begin(), parameters.extent.end());
 
         auto &fileData = getFileData(file, IfFileNotOpen::ThrowError);
+
+#define HAS_BP5_BLOSC2_BUG                                                     \
+    (ADIOS2_VERSION_MAJOR * 100 + ADIOS2_VERSION_MINOR == 209 &&               \
+     ADIOS2_VERSION_PATCH <= 1)
+#if HAS_BP5_BLOSC2_BUG
+        std::string engineType = fileData.getEngine().Type();
+        std::transform(
+            engineType.begin(),
+            engineType.end(),
+            engineType.begin(),
+            [](unsigned char c) { return std::tolower(c); });
+        if (!printedWarningsAlready.blosc2bp5 && engineType == "bp5writer")
+        {
+            for (auto const &op : operators)
+            {
+                std::string operatorType = op.op.Type();
+                std::transform(
+                    operatorType.begin(),
+                    operatorType.end(),
+                    operatorType.begin(),
+                    [](unsigned char c) { return std::tolower(c); });
+                if (operatorType == "blosc")
+                {
+                    std::cerr << &R"(
+[Warning] Use BP5+Blosc with care in ADIOS2 v2.9.0 and v2.9.1.
+Unreadable data might be created, to mitigate either deactivate Blosc or use BP4+Blosc.
+For further details see
+https://github.com/ornladios/ADIOS2/issues/3504.
+                    )"[1] << std::endl;
+                    printedWarningsAlready.blosc2bp5 = true;
+                }
+            }
+        }
+#endif
+#undef HAS_BP5_BLOSC2_BUG
+
         switchAdios2VariableType<detail::VariableDefiner>(
             parameters.dtype, fileData.m_IO, varName, operators, shape);
         fileData.invalidateVariablesMap();

test/SerialIOTest.cpp

@@ -80,10 +80,24 @@ std::vector<std::string> testedFileExtensions()
 {
     auto allExtensions = getFileExtensions();
     auto newEnd = std::remove_if(
-        allExtensions.begin(), allExtensions.end(), [](std::string const &ext) {
+        allExtensions.begin(),
+        allExtensions.end(),
+        []([[maybe_unused]] std::string const &ext) {
+#if openPMD_HAVE_ADIOS2
+#define HAS_ADIOS_2_9 (ADIOS2_VERSION_MAJOR * 100 + ADIOS2_VERSION_MINOR >= 209)
+#if HAS_ADIOS_2_9
+            // sst and ssc need a receiver for testing
+            // bp5 is already tested via bp
+            return ext == "sst" || ext == "ssc" || ext == "bp5";
+#else
             // sst and ssc need a receiver for testing
             // bp4 is already tested via bp
             return ext == "sst" || ext == "ssc" || ext == "bp4";
+#endif
+#undef HAS_ADIOS_2_9
+#else
+            return false;
+#endif
         });
     return {allExtensions.begin(), newEnd};
 }