Quash a few 'warning: comparison of function 'compression_decode_buffer' not equal to a null pointer is always true [-Wtautologica l-pointer-compare]'

[hintonda]

Summary

Quash several warnings of this type using clang's suggested fix:

[2741/3631] Building CXX object tools/lldb/source/Plugins/Process/gdb-remote/CMakeFiles/lldbPluginProcessGDBRemote.dir/GDBRemoteCommunication.cpp.o
/Users/dhinton/projects/llvm_project/llvm/tools/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp:603:7: warning: comparison of function 'compression_decode_buffer' not equal to a null pointer is always true [-Wtautological-pointer-compare]

if (compression_decode_buffer != NULL &&
    ^~~~~~~~~~~~~~~~~~~~~~~~~    ~~~~

/Users/dhinton/projects/llvm_project/llvm/tools/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp:603:7: note: prefix with the address-of operator to silence this warning

if (compression_decode_buffer != NULL &&
    ^
    &

source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp

if (decompressed_buffer == nullptr) {
       m_bytes.erase(0, size_of_first_packet);
       return false;
     }
   }
 
 #if defined(HAVE_LIBCOMPRESSION)
   // libcompression is weak linked so check that compression_decode_buffer() is
   // available
-  if (compression_decode_buffer != NULL &&
+  if (&compression_decode_buffer != NULL &&
       (m_compression_type == CompressionType::ZlibDeflate ||
        m_compression_type == CompressionType::LZFSE ||
        m_compression_type == CompressionType::LZ4)) {
     compression_algorithm compression_type;
     if (m_compression_type == CompressionType::LZFSE)
       compression_type = COMPRESSION_LZFSE;
     else if (m_compression_type == CompressionType::ZlibDeflate)
       compression_type = COMPRESSION_ZLIB;

source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp

 void GDBRemoteCommunicationClient::MaybeEnableCompression(
     std::vector<std::string> supported_compressions) {
   CompressionType avail_type = CompressionType::None;
   std::string avail_name;
 
 #if defined(HAVE_LIBCOMPRESSION)
   // libcompression is weak linked so test if compression_decode_buffer() is
   // available
-  if (compression_decode_buffer != NULL &&
+  if (&compression_decode_buffer != NULL &&
       avail_type == CompressionType::None) {
     for (auto compression : supported_compressions) {
       if (compression == "lzfse") {
         avail_type = CompressionType::LZFSE;
         avail_name = compression;
         break;
       }
     }
   }
 #endif
 
 #if defined(HAVE_LIBCOMPRESSION)
   // libcompression is weak linked so test if compression_decode_buffer() is
   // available
-  if (compression_decode_buffer != NULL &&
+  if (&compression_decode_buffer != NULL &&
       avail_type == CompressionType::None) {
     for (auto compression : supported_compressions) {
       if (compression == "zlib-deflate") {
         avail_type = CompressionType::ZlibDeflate;
         avail_name = compression;
         break;
       }
     }
for (auto compression : supported_compressions) {
       }
     }
   }
 #endif
 
 #if defined(HAVE_LIBCOMPRESSION)
   // libcompression is weak linked so test if compression_decode_buffer() is
   // available
-  if (compression_decode_buffer != NULL &&
+  if (&compression_decode_buffer != NULL &&
       avail_type == CompressionType::None) {
     for (auto compression : supported_compressions) {
       if (compression == "lz4") {
         avail_type = CompressionType::LZ4;
         avail_name = compression;
         break;
       }
     }
   }
 #endif
 
 #if defined(HAVE_LIBCOMPRESSION)
   // libcompression is weak linked so test if compression_decode_buffer() is
   // available
-  if (compression_decode_buffer != NULL &&
+  if (&compression_decode_buffer != NULL &&
       avail_type == CompressionType::None) {
     for (auto compression : supported_compressions) {
       if (compression == "lzma") {
         avail_type = CompressionType::LZMA;
         avail_name = compression;
         break;
       }
     }