A weird error in in LevelDB while compiling a custom layer of caffe

Question

#include <leveldb/status.h>
#include <leveldb/db.h>
#include <leveldb/write_batch.h>
...
int arg_offset = 0;
leveldb::DB* db1;
leveldb::Options options;
options.error_if_exists = true;
options.create_if_missing = true;
options.write_buffer_size = 268435456;
leveldb::WriteBatch* batch;
...
if (db_backend == "leveldb") 
{  
    // leveldb
    LOG(INFO) << "Opening leveldb " << argv[arg_offset+2];
    leveldb::Status status1 = leveldb::DB::Open(options, argv[arg_offset+2], &db1);
    CHECK(status1.ok()) << "Failed to open leveldb " << argv[arg_offset+2];
    batch = new leveldb::WriteBatch();
}

The above code snippet generates the following errors

$ g++ tools/convert_imageset_and_disparity.cpp -MMD -MP -pthread -fPIC -DCAFFE_VERSION=1.0.0-rc5 -DNDEBUG -O2 -DUSE_OPENCV -DUSE_LEVELDB -DUSE_LMDB -DWITH_PYTHON_LAYER -I/usr/include/python3.5m -I/usr/lib/python3.5/dist-packages/numpy/core/include -I/usr/local/include -I/usr/include/hdf5/serial -I/usr/include -I.build_release/src -I./src -I./include -I/usr/local/cuda-9.0/include -Wall -Wno-sign-compare -c -o .build_release/tools/convert_imageset_and_disparity.o 2> .build_release/tools/convert_imageset_and_disparity.o.warnings.txt \
    || (cat .build_release/tools/convert_imageset_and_disparity.o.warnings.txt; exit 1)



error: expected unqualified-id before ‘int’
         leveldb::Status status1 = leveldb::DB::Open(options, argv[arg_offset+2], &db1);
 -----------------^

error: ‘status1’ was not declared in this scope
         CHECK(status1.ok()) << "Failed to open leveldb " << argv[arg_offset+2];
---------------^

Compiler version :

$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.4.0-6ubuntu1~16.04.9' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.9)

LevelDB is installed using sudo apt-get install libleveldb-dev

The same library is compiling a similar call to leveldb in another cpp file and it gets compiled successfully

void LevelDB::Open(const string& source, Mode mode) {
  leveldb::Options options;
  options.block_size = 65536;
  options.write_buffer_size = 268435456;
  options.max_open_files = 100;
  options.error_if_exists = mode == NEW;
  options.create_if_missing = mode != READ;
  leveldb::Status status = leveldb::DB::Open(options, source, &db_);
  CHECK(status.ok()) << "Failed to open leveldb " << source
                     << std::endl << status.ToString();
  LOG(INFO) << "Opened leveldb " << source;
}

Can someone help me to debug this error: expected unqualified-id ?

An excellent tutorial on How to use LevelDB is listed here.

Start removing pieces from that line to see what causes the error. Looks to me like the compiler doesn't know one of the symbols in that line (which is why it says 'int') — ZivS, Mar 16 '18 at 18:16
I just checked the ASCII character for that line; my implementation (which is not working) and the original implementation (which is working) and there is no 'vague' character in any of two implementations. — Khurram Amin, Mar 16 '18 at 18:29
I meant that instead of calling `leveldb::Status status1 = leveldb::DB::Open(options, argv[arg_offset+2], &db1);`, you should call: `auto status1 = leveldb::DB::Open(nullptr, nullptr, nullptr);` or something similar to make sure that the call works and then make sure each argument is valid, etc... — ZivS, Mar 16 '18 at 20:53
Some other header that `#define`s `Status` to something like `int`, perhaps? — bogdan, Mar 16 '18 at 20:55

Khurram Amin · Accepted Answer · 2018-03-17T16:17:56.040

Finally I was able to (atleast) resolve the compilation error. Here are the changes that I made:

changed leveldb::Status status1 = leveldb::DB::Open(options, argv[arg_offset+2], &db1) to auto status1 = leveldb::DB::Open(options, argv[arg_offset+2], &db1) Thanks @ZivS for pointing it out.
changed Makefile from LIBRARIES += glog gflags protobuf leveldb snappy \ lmdb boost_system boost_filesystem hdf5_hl hdf5 m \ opencv_core opencv_highgui opencv_imgproc opencv_imgcodecs opencv_videoio to LIBRARIES += glog gflags protobuf leveldb snappy \ lmdb boost_system boost_filesystem hdf5_hl hdf5 m \ opencv_core opencv_highgui opencv_imgproc opencv_imgcodecs opencv_videoio X11
Then finally compiled with -std=c++11 flag

The code was able to compile. Will update once I load the LevelDB using the built object.

Edit 2 Compiled code is running successfully.

A weird error in in LevelDB while compiling a custom layer of caffe

1 Answers1