在 PostgreSQL C 扩展中包含头文件

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【中文标题】在 PostgreSQL C 扩展中包含头文件【英文标题】：Including header files in a PostgreSQL C extension 【发布时间】：2018-08-18 07:19:10 【问题描述】：

我在 seal_diff_cpp.cpp 文件中有我的 C 扩展的代码：

extern "C"  // C Headers must be inside exter "C"   block.
#include <postgres.h>
#include <utils/rel.h>
#include <fmgr.h>
#include <utils/array.h>
#include <utils/builtins.h>
#include <catalog/pg_type.h>
#include <stdlib.h>
#include <stdint.h>

PG_MODULE_MAGIC;


// CPP Header must be outside extern "C"   block.
#include <string>
#include <vector>
#include <iostream>
#include <fstream>
#include <sstream>
#include <iterator> // For the ostream_iterator

// External projects c++ libraries compiled and linked on running 'make'.
#include <seal/seal.h>
#include <cppcodec/base64_rfc4648.hpp>

// CPP function can be declared and used inside or outside extern "C"   block.
std::stringstream dec(std::string st)
        // Decode the base64 string into a stringstream 
        auto decodeBase64 = cppcodec::base64_rfc4648::decode(st);
        std::stringstream decodeBase64SS;
        std::move(decodeBase64.begin(), decodeBase64.end(), std::ostream_iterator<unsigned char>(decodeBase64SS));

        return decodeBase64SS;


std::string enc(std::string st)

        // Create a vector to hold the raw data
        std::vector<uint8_t> encodeStream;

        // Push all the characters from the raw data string into the vector
        for (auto &ch : st)
                encodeStream.push_back((unsigned char&&)(ch));
        

        // Encode the vector as base64 string
        std::string encodeBase64 = cppcodec::base64_rfc4648::encode(encodeStream);
        encodeStream.clear();
        return encodeBase64;




std::string seal_diff_operation(std::string decodedLocalEncParamTmp, std::string decodedLocalTmp, std::string decodedLocalTmp)
        std::stringstream decodedLocalEncParam;
        decodedLocalEncParam.str(decodedLocalEncParamTmp);
        std::stringstream decodedLocalT1;
        decodedLocalT1.str(decodedLocalTmp);
        std::stringstream decodedLocalT2;
        decodedLocalT2.str(decodedLocalTmp);

        // Execute seal library operations
        // Load the ecryption parameters
        seal::EncryptionParameters IntegerEncryptorParms;
        IntegerEncryptorParms.load(decodedLocalEncParam);
        // Set Context and evaluator objects
        seal::SEALContext context(IntegerEncryptorParms);
        seal::Evaluator evaluator(context);
        // Set the Encoder parameters
        seal::IntegerEncoder encoder(context.plain_modulus());

        // Create Ciphertexts and load Chipertext information into them
        seal::Ciphertext number1Encoded;
        seal::Ciphertext number2Encoded;
        seal::Ciphertext diffEncodedResult;
        number1Encoded.load(decodedLocalT1);
        number2Encoded.load(decodedLocalT2);

        // Do the diff operation on the Ciphertexts and prepare the result for output
        evaluator.sub(number1Encoded, number2Encoded, diffEncodedResult);
        std::stringstream encResult;
        diffEncodedResult.save(encResult);

        std::string output = enc(encResult.str());

        return output;



extern "C"  // PostgreSQL functions be inside extern "C"   block. 
Datum seal_diff_cpp(PG_FUNCTION_ARGS)

        // Get the Parameters
        text *t1 = PG_GETARG_TEXT_PP(0);
        text *t2 = PG_GETARG_TEXT_PP(1);
        text *encParam = PG_GETARG_TEXT_PP(2);
        std::string localT1;
        std::string localT2;
        std::string localEncParam;
        localT1 = text_to_cstring(t1);
        localT2 = text_to_cstring(t2);
        localEncParam = text_to_cstring(encParam);

        // Decode the parameters 
        std::stringstream decodedLocalT1 = dec(localT1);
        std::stringstream decodedLocalT2 = dec(localT2);
        std::stringstream decodedLocalEncParam = dec(localEncParam);

        // Encode the parameters
        std::string encodedLocalT1 = enc(decodedLocalT1.str());
        //std::string encodedLocalT1 = enc(encResult.str());
        std::string encodedLocalT2 = enc(decodedLocalT2.str());
        //std::string outputParam = seal_diff_operation(decodedLocalEncParam.str(), decodedLocalT1.str(), decodedLocalT2.str());

        // Returns Text 
        PG_RETURN_TEXT_P(cstring_to_text_with_len(localT1.c_str(), localT1.size()));

;
PG_FUNCTION_INFO_V1(seal_diff_cpp);

我使用这个又快又脏的Makefile 来创建我的.so 文件：

MODULES = seal_diff_cpp

PG_CONFIG = /usr/pgsql-10/bin/pg_config
PGXS = $(shell $(PG_CONFIG) --pgxs)
INCLUDEDIR = $(shell $(PG_CONFIG) --includedir-server)
INCLUDE_SEAL = /usr/local/include/seal
INCLUDE_SEAL_LIB = /usr/local/lib
INCLUDE_CPPCODEC = /usr/local/include/cppcodec
CXX = g++
CXXFLAGS = -std=c++17 -fPIC -Wall -Werror -g -O0 -pthread \
        -I$(INCLUDEDIR) -L$(INCLUDE_SEAL_LIB) -l libseal.a -I$(INCLUDE_SEAL) -I$(INCLUDE_CPPCODEC)
include $(PGXS)
seal_diff_cpp.so: seal_diff_cpp.o
        $(CXX) -shared -o seal_diff_cpp.so seal_diff_cpp.o

seal_diff_cpp.o: seal_diff_cpp.cpp
         $(CXX) $(CXXFLAGS) -o seal_diff_cpp.o -c seal_diff_cpp.cpp

当我尝试将我的 C 扩展名复制到 /usr/pgsql-10/lib/ 文件夹后添加

-- Drop the function first, needed when changing return type
DROP FUNCTION IF EXISTS public.seal_diff_cpp(CHARACTER VARYING, CHARACTER VARYING, CHARACTER VARYING);

-- Create the new function
CREATE OR REPLACE FUNCTION 
   seal_diff_cpp(CHARACTER VARYING, CHARACTER VARYING, CHARACTER VARYING) RETURNS CHARACTER VARYING AS 'seal_diff_cpp' 
LANGUAGE C STRICT;

我得到错误：

错误：无法加载库“/usr/pgsql-10/lib/seal_diff_cpp.so”： /usr/pgsql-10/lib/seal_diff_cpp.so：未定义符号： _ZN4seal9Evaluator3subERNS_10CiphertextERKS1_SQL状态：XX000

这个_ZN4seal9Evaluator3subERNS_10CiphertextERKS1_ 是因为使用了seal::&lt;some parameter&gt; 而创建的，#include &lt;seal/seal.h&gt; 在那里所以不会发生这样的错误。 SEAL 库是安装到/usr/local/include/seal 的外部库，它的libseal.a 安装到/usr/local/lib/。

seal:: 对象的第一个声明发生错误，我没有任何问题/错误使用我的 Makefile 将其编译到所需的 seal_diff_cpp.so 文件中。当我注释所有 SEAL 代码时，扩展程序可以与 /usr/local/include/cppcodec 下的第二个外部库 (#include &lt;cppcodec/base64_rfc4648.hpp&gt;) 完美运行。

我在.cpp 文件或Makefile 中的印章库有什么问题吗？我是否需要将外部SEAL 和cppcodec 库安装到/usr/pgsql-10/include/ 或其他pgsql-10 路径中？感觉#include &lt;seal/seal.h&gt;不行了。

更新

按照 Alan Britles 的建议更改我的 Makefile 并运行 make 后，我得到了这个输出，显示链接没有错误：

g++ -Wl,--no-undefined -std=c++17 -fPIC -Wall -Werror -g -O0 -pthread -I/usr/pgsql-10/include/server -I/usr/local/include/seal -I/usr/local/include/cppcodec -o seal_diff_cpp.o -c seal_diff_cpp.cpp g++ -L/usr/pgsql- 10/lib -L/usr/lib64 -Wl,--按需 -Wl,-rpath,'/usr/pgsql-10/lib',--enable-new-dtags -shared -o seal_diff_cpp.so seal_diff_cpp.o

使用nm -gC seal_diff_cpp.so | grep "seal"：我得到这个输出：

000000000000e641 T pg_finfo_seal_diff_cpp
000000000000e26c T seal_diff_cpp
000000000000de73 T seal_diff_operation(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >)
                 U seal::Ciphertext::load(std::istream&)
                 U seal::Ciphertext::operator=(seal::Ciphertext const&)
000000000000f3b0 W seal::Ciphertext::Ciphertext()
000000000000f3b0 W seal::Ciphertext::Ciphertext()
000000000000f42c W seal::Ciphertext::~Ciphertext()
000000000000f42c W seal::Ciphertext::~Ciphertext()
                 U seal::SEALContext::SEALContext(seal::EncryptionParameters const&)
000000000000f1e6 W seal::SEALContext::~SEALContext()
000000000000f1e6 W seal::SEALContext::~SEALContext()
                 U seal::IntegerEncoder::IntegerEncoder(seal::SmallModulus const&, unsigned long)
                 U seal::IntegerEncoder::~IntegerEncoder()
000000000000eb80 W seal::MemoryPoolHandle::MemoryPoolHandle()
000000000000eb80 W seal::MemoryPoolHandle::MemoryPoolHandle()
000000000000eabe W seal::MemoryPoolHandle::~MemoryPoolHandle()
000000000000eabe W seal::MemoryPoolHandle::~MemoryPoolHandle()
                 U seal::EncryptionParameters::load(std::istream&)
                 U seal::EncryptionParameters::EncryptionParameters()
000000000000ebd2 W seal::EncryptionParameters::~EncryptionParameters()
000000000000ebd2 W seal::EncryptionParameters::~EncryptionParameters()
000000000000effc W seal::util::BaseConverter::~BaseConverter()
000000000000effc W seal::util::BaseConverter::~BaseConverter()
000000000000f166 W seal::util::SmallNTTTables::~SmallNTTTables()
000000000000f166 W seal::util::SmallNTTTables::~SmallNTTTables()
000000000000eba0 W seal::util::Modulus::~Modulus()
000000000000eba0 W seal::util::Modulus::~Modulus()
000000000000e9bc W seal::util::Pointer::release()
000000000000e986 W seal::util::Pointer::Pointer()
000000000000e986 W seal::util::Pointer::Pointer()
000000000000ea66 W seal::util::Pointer::~Pointer()
000000000000ea66 W seal::util::Pointer::~Pointer()
                 U seal::BigPoly::~BigPoly()
                 U seal::BigUInt::~BigUInt()
000000000000ec1c W seal::Evaluator::sub(seal::Ciphertext const&, seal::Ciphertext const&, seal::Ciphertext&)
                 U seal::Evaluator::sub(seal::Ciphertext&, seal::Ciphertext const&)
                 U seal::Evaluator::Evaluator(seal::SEALContext const&)
000000000000f276 W seal::Evaluator::~Evaluator()
000000000000f276 W seal::Evaluator::~Evaluator()
0000000000011c16 W __gnu_cxx::new_allocator<seal::SmallModulus>::deallocate(seal::SmallModulus*, unsigned long)
0000000000010afe W __gnu_cxx::new_allocator<seal::SmallModulus>::~new_allocator()
0000000000010afe W __gnu_cxx::new_allocator<seal::SmallModulus>::~new_allocator()
0000000000013e54 W __gnu_cxx::new_allocator<seal::util::SmallNTTTables>::deallocate(seal::util::SmallNTTTables*, unsigned long)
000000000001383a W __gnu_cxx::new_allocator<seal::util::SmallNTTTables>::~new_allocator()
000000000001383a W __gnu_cxx::new_allocator<seal::util::SmallNTTTables>::~new_allocator()
                 U seal::Ciphertext::save(std::ostream&) const
000000000000ebfe W seal::SEALContext::plain_modulus() const
000000000000ebc0 W seal::EncryptionParameters::plain_modulus() const
000000000000ff92 W std::allocator<seal::SmallModulus>::~allocator()
000000000000ff92 W std::allocator<seal::SmallModulus>::~allocator()
00000000000114fe W std::allocator<seal::util::SmallNTTTables>::~allocator()
00000000000114fe W std::allocator<seal::util::SmallNTTTables>::~allocator()
000000000000eb20 W std::shared_ptr<seal::util::MemoryPool>::shared_ptr(decltype(nullptr))
000000000000eb04 W std::shared_ptr<seal::util::MemoryPool>::shared_ptr()
000000000000eaa2 W std::shared_ptr<seal::util::MemoryPool>::~shared_ptr()
000000000000eaa2 W std::shared_ptr<seal::util::MemoryPool>::~shared_ptr()
0000000000013881 W void std::_Destroy_aux<false>::__destroy<seal::util::SmallNTTTables*>(seal::util::SmallNTTTables*, seal::util::SmallNTTTables*)
0000000000011c06 W void std::_Destroy_aux<true>::__destroy<seal::SmallModulus*>(seal::SmallModulus*, seal::SmallModulus*)
000000000000eb40 W std::__shared_ptr<seal::util::MemoryPool, (__gnu_cxx::_Lock_policy)2>::__shared_ptr()
000000000000ea82 W std::__shared_ptr<seal::util::MemoryPool, (__gnu_cxx::_Lock_policy)2>::~__shared_ptr()
000000000000ea82 W std::__shared_ptr<seal::util::MemoryPool, (__gnu_cxx::_Lock_policy)2>::~__shared_ptr()
000000000000ffae W std::_Vector_base<seal::SmallModulus, std::allocator<seal::SmallModulus> >::_Vector_impl::~_Vector_impl()
000000000000ffae W std::_Vector_base<seal::SmallModulus, std::allocator<seal::SmallModulus> >::_Vector_impl::~_Vector_impl()
0000000000010060 W std::_Vector_base<seal::SmallModulus, std::allocator<seal::SmallModulus> >::_M_deallocate(seal::SmallModulus*, unsigned long)
0000000000010028 W std::_Vector_base<seal::SmallModulus, std::allocator<seal::SmallModulus> >::_M_get_Tp_allocator()
000000000000ffca W std::_Vector_base<seal::SmallModulus, std::allocator<seal::SmallModulus> >::~_Vector_base()
000000000000ffca W std::_Vector_base<seal::SmallModulus, std::allocator<seal::SmallModulus> >::~_Vector_base()
000000000001073a W std::_Vector_base<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::_Vector_impl::~_Vector_impl()
000000000001073a W std::_Vector_base<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::_Vector_impl::~_Vector_impl()
000000000001151a W std::_Vector_base<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::_M_deallocate(seal::util::SmallNTTTables*, unsigned long)
00000000000107b4 W std::_Vector_base<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::_M_get_Tp_allocator()
0000000000010756 W std::_Vector_base<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::~_Vector_base()
0000000000010756 W std::_Vector_base<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::~_Vector_base()
0000000000010b2f W std::allocator_traits<std::allocator<seal::SmallModulus> >::deallocate(std::allocator<seal::SmallModulus>&, seal::SmallModulus*, unsigned long)
0000000000013845 W std::allocator_traits<std::allocator<seal::util::SmallNTTTables> >::deallocate(std::allocator<seal::util::SmallNTTTables>&, seal::util::SmallNTTTables*, unsigned long)
000000000000f574 W std::vector<seal::SmallModulus, std::allocator<seal::SmallModulus> >::~vector()
000000000000f574 W std::vector<seal::SmallModulus, std::allocator<seal::SmallModulus> >::~vector()
000000000000fbbe W std::vector<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::~vector()
000000000000fbbe W std::vector<seal::util::SmallNTTTables, std::allocator<seal::util::SmallNTTTables> >::~vector()
0000000000013873 W seal::util::SmallNTTTables* std::__addressof<seal::util::SmallNTTTables>(seal::util::SmallNTTTables&)
0000000000013e76 W void std::_Destroy<seal::util::SmallNTTTables>(seal::util::SmallNTTTables*)
0000000000010b09 W void std::_Destroy<seal::SmallModulus*>(seal::SmallModulus*, seal::SmallModulus*)
0000000000010036 W void std::_Destroy<seal::SmallModulus*, seal::SmallModulus>(seal::SmallModulus*, seal::SmallModulus*, std::allocator<seal::SmallModulus>&)
000000000001154f W void std::_Destroy<seal::util::SmallNTTTables*>(seal::util::SmallNTTTables*, seal::util::SmallNTTTables*)
00000000000107c2 W void std::_Destroy<seal::util::SmallNTTTables*, seal::util::SmallNTTTables>(seal::util::SmallNTTTables*, seal::util::SmallNTTTables*, std::allocator<seal::util::SmallNTTTables>&)

所以我猜 SEAL 库已正确链接，但我确实有一些重要的符号带有未定义 (U)，因此我仍然从 PostgreSQL 收到相同的错误。但是为什么这些符号被标记为未定义？

【问题讨论】：

尝试在你的makefile中使用这个CXXFLAGS = -std=c++17 -fPIC -Wall -Werror -g -O0 -pthread \ -I$(INCLUDEDIR) -L$(INCLUDE_SEAL_LIB) -lseal -I$(INCLUDE_SEAL) -I$(INCLUDE_CPPCODEC)，并使用objdump检查符号是否在libseal.a和so文件中 尝试将--no-undefined 添加到您的链接命令中，这将使 GCC 在链接时报告未定义的符号，而不是让它们在运行时潜入您 完成后，将库链接器标志从编译命令移动到链接命令 @leiyc 我已经更新了我的帖子，看起来 SEAL 库链接正确。 @leiyc 我确实有一些带有U 标志的符号。如果我没记错的话，这意味着它们是未定义的。 【参考方案1】：

GCC 有一个在链接时报告未定义符号的选项，默认情况下共享库是关闭的。通过--no-undefined 开关打开它。当存在未定义的符号而不是在运行时报告它们时，这将使链接器失败。

您的问题是您将库链接命令传递给编译命令（它们被忽略）而不是链接命令。尝试按如下方式修改您的 make 文件：

CXXFLAGS = -std=c++17 -fPIC -Wall -Werror -g -O0 -pthread \
        -I$(INCLUDEDIR) -I$(INCLUDE_SEAL) -I$(INCLUDE_CPPCODEC)
LDFLAGS = -L$(INCLUDE_SEAL_LIB) -l libseal.a -pthread

seal_diff_cpp.so: seal_diff_cpp.o
        $(CXX) $(LDFLAGS) -shared -o seal_diff_cpp.so seal_diff_cpp.o

seal_diff_cpp.o: seal_diff_cpp.cpp
         $(CXX) $(CXXFLAGS) -o seal_diff_cpp.o -c seal_diff_cpp.cpp

注意：不将-pthread 传递给链接器也可能会导致一些微妙的问题。

【讨论】：

我已添加将最后一行更改为$(CXX) -Wl,--no-undefined $(CXXFLAGS) -o seal_diff_cpp.o -c seal_diff_cpp.cpp，使用make 创建此输出g++ -Wl,--no-undefined -std=c++17 -fPIC -Wall -Werror -g -O0 -pthread -I/usr/pgsql-10/include/server -I/usr/local/include/seal -I/usr/local/include/cppcodec -o seal_diff_cpp.o -c seal_diff_cpp.cpp g++ -L/usr/pgsql-10/lib -L/usr/lib64 -Wl,--as-needed -Wl,-rpath,'/usr/pgsql-10/lib',--enable-new-dtags -shared -o seal_diff_cpp.so seal_diff_cpp.o @TalG 您需要将此标志添加到链接器命令而不是编译器命令 @AlanBritles，谢谢，现在我得到了错误:)。但我仍然不知道我为什么要得到它们。我已经链接并包含了所有内容。 您是否按照我的建议将-l libseal.a 移至您的链接器命令？ @AlanBritles，我在我的Makefile中使用你的版本@

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