Fix precision-losing type conversion

Author: franzpoeschel

src/IO/JSON/JSONIOHandlerImpl.cpp

@@ -967,9 +967,10 @@ namespace
         {
             T *casted = static_cast<T *>(ptr);
             size_t flattenedExtent = std::accumulate(
-                extent.begin(), extent.end(), 1, [](size_t left, size_t right) {
-                    return left * right;
-                });
+                extent.begin(),
+                extent.end(),
+                size_t(1),
+                [](size_t left, size_t right) { return left * right; });
             std::fill_n(casted, flattenedExtent, T{});
         }
 
@@ -1537,14 +1538,16 @@ std::shared_ptr<nlohmann::json> JSONIOHandlerImpl::obtainJsonContents(File file)
     }
     // read from file
     auto fh = getFilehandle(file, Access::READ_ONLY);
+    auto &fh_with_precision =
+        *fh >> std::setprecision(std::numeric_limits<double>::digits10 + 1);
     std::shared_ptr<nlohmann::json> res = std::make_shared<nlohmann::json>();
     switch (m_fileFormat)
     {
     case FileFormat::Json:
-        *fh >> *res;
+        fh_with_precision >> *res;
         break;
     case FileFormat::Toml:
-        *res = openPMD::json::tomlToJson(toml::parse(*fh, *file));
+        *res = openPMD::json::tomlToJson(toml::parse(fh_with_precision, *file));
         break;
     }
     VERIFY(fh->good(), "[JSON] Failed reading from a file.");

test/SerialIOTest.cpp

@@ -1240,9 +1240,9 @@ inline void dtype_test(
     std::optional<std::string> activateTemplateMode = {})
 {
     bool test_long_double =
-        (backend != "json" && backend != "toml") || sizeof(long double) <= 8;
+        (backend != "json" || sizeof(long double) <= 8) && backend != "toml";
     bool test_long_long =
-        (backend != "json" && backend != "toml") || sizeof(long long) <= 8;
+        (backend != "json" || sizeof(long long) <= 8) && backend != "toml";
     {
         Series s = activateTemplateMode.has_value()
             ? Series(
@@ -1437,7 +1437,10 @@ inline void dtype_test(
     REQUIRE(s.getAttribute("short").dtype == Datatype::SHORT);
     REQUIRE(s.getAttribute("int").dtype == Datatype::INT);
     REQUIRE(s.getAttribute("long").dtype == Datatype::LONG);
-    REQUIRE(s.getAttribute("longlong").dtype == Datatype::LONGLONG);
+    if (test_long_long)
+    {
+        REQUIRE(s.getAttribute("longlong").dtype == Datatype::LONGLONG);
+    }
     REQUIRE(s.getAttribute("ushort").dtype == Datatype::USHORT);
     REQUIRE(s.getAttribute("uint").dtype == Datatype::UINT);
     REQUIRE(s.getAttribute("ulong").dtype == Datatype::ULONG);
@@ -1449,7 +1452,10 @@ inline void dtype_test(
     REQUIRE(s.getAttribute("vecShort").dtype == Datatype::VEC_SHORT);
     REQUIRE(s.getAttribute("vecInt").dtype == Datatype::VEC_INT);
     REQUIRE(s.getAttribute("vecLong").dtype == Datatype::VEC_LONG);
-    REQUIRE(s.getAttribute("vecLongLong").dtype == Datatype::VEC_LONGLONG);
+    if(test_long_long)
+    {
+        REQUIRE(s.getAttribute("vecLongLong").dtype == Datatype::VEC_LONGLONG);
+    }
     REQUIRE(s.getAttribute("vecUShort").dtype == Datatype::VEC_USHORT);
     REQUIRE(s.getAttribute("vecUInt").dtype == Datatype::VEC_UINT);
     REQUIRE(s.getAttribute("vecULong").dtype == Datatype::VEC_ULONG);