Show reasons a POSIX file cannot be read

tiledb/sm/filesystem/mem_filesystem.cc

@@ -31,6 +31,7 @@
  */
 
 #include <algorithm>
+#include <format>
 #include <mutex>
 #include <sstream>
 #include <unordered_set>
@@ -183,8 +184,12 @@ class MemFilesystem::File : public MemFilesystem::FSNode {
     assert(buffer);
 
     if (offset + nbytes > size_)
-      return LOG_STATUS(
-          Status_MemFSError("Cannot read from file; Read exceeds file size"));
+      return LOG_STATUS(Status_MemFSError(std::format(
+          "Cannot read from file; Read exceeds file size: offset {} nbytes {} "
+          "size_ {}",
+          offset,
+          nbytes,
+          size_)));
 
     memcpy(buffer, (char*)data_ + offset, nbytes);
     return Status::Ok();

tiledb/sm/filesystem/posix.cc

@@ -32,10 +32,10 @@
 
 #ifndef _WIN32
 
-#include "tiledb/sm/filesystem/posix.h"
 #include "tiledb/common/filesystem/directory_entry.h"
 #include "tiledb/common/logger.h"
 #include "tiledb/common/stdx_string.h"
+#include "tiledb/sm/filesystem/posix.h"
 #include "tiledb/sm/misc/constants.h"
 #include "tiledb/sm/misc/tdb_math.h"
 #include "uri.h"
@@ -47,6 +47,7 @@
 #include <unistd.h>
 
 #include <algorithm>
+#include <format>
 #include <fstream>
 #include <future>
 #include <iostream>
@@ -273,8 +274,15 @@ void Posix::read(
   auto path = uri.to_path();
   uint64_t file_size;
   this->file_size(URI(path), &file_size);
-  if (offset + nbytes > file_size)
-    throw IOError("Cannot read from file; Read exceeds file size");
+  if (offset + nbytes > file_size) {
+    throw IOError(std::format(
+        "Cannot read from file; Read exceeds file size: offset {}, nbytes {}, "
+        "file_size {}, URI {}",
+        offset,
+        nbytes,
+        file_size,
+        uri.to_path()));
+  }
 
   // Open file
   int fd = open(path.c_str(), O_RDONLY);