Fix H5Zzstd error reporting and decompressed size behavior (JuliaIO#1151

)

* Fix H5Zzstd error reporting and decompressed size behavior

* Remove commented out code

* Use async so that callback function returns properly

* Fix formatting

filters/H5Zzstd/src/H5Zzstd.jl

@@ -38,6 +38,9 @@ function H5Z_filter_zstd(
             #decompresssion
 
             decompSize = LibZstd.ZSTD_getDecompressedSize(inbuf, origSize)
+            if decompSize == 0
+                error("zstd_h5plugin: Cannot retrieve decompressed chunk size")
+            end
             outbuf = Libc.malloc(decompSize)
             if outbuf == C_NULL
                 error(
@@ -83,11 +86,11 @@ function H5Z_filter_zstd(
     catch e
         #  "In the case of failure, the return value is 0 (zero) and all pointer arguments are left unchanged."
         ret_value = Csize_t(0)
-        @error "H5Zzstd Non-Fatal ERROR: " err
-        display(stacktrace(catch_backtrace()))
+        # Output Julia error via async so we do not task switch during callback
+        @async @error "H5Zzstd Non-Fatal ERROR: " exception = (e, catch_backtrace())
     finally
         if outbuf != C_NULL
-            free(outbuf)
+            Libc.free(outbuf)
         end
     end # try catch finally
     return Csize_t(ret_value)