c++ - Codelite 使用 libpqxx 连接示例和 g++ 在 macOS 上失败
问题描述
我已经尝试过make和cmake来编译和部署libpqxx，但简单的代码似乎不起作用。https://github.com/jtv/libpqxx/blob/master/BUILDING-configure.md。我使用官方 Git repo 上的说明安装了该库，但在 Codelite 项目中的构建步骤仍然存在问题。
Codelite项目配置：
- Makefile 生成器 默认
- 编译器 GCC
- 编译器选项：-g;-O0;-Wall -lpqxx -lpq
当我列出已安装的库时，我可以看到 libpqxx 库：
lrwxr-xr-x 1 thomaspeters staff 48 Aug 17 22:50 postgres_ext.h -> ../Cellar/postgresql/13.4/include/postgres_ext.h
lrwxr-xr-x 1 thomaspeters staff 44 Aug 17 22:50 postgresql -> ../Cellar/postgresql/13.4/include/postgresql
drwxr-xr-x 129 root staff 4128 Sep 12 02:05 pqxx
我安装了postgres客户端库和pqxx库。注意所有权设置为root。这是权限问题吗？
#include <iostream>
#include <pqxx/pqxx>
using namespace std;
using namespace pqxx;
int main(int argc, char* argv[]) {
try {
connection C("dbname = testdb user = postgres password = cohondob \
hostaddr = 127.0.0.1 port = 5432");
if (C.is_open()) {
cout << "Opened database successfully: " << C.dbname() << endl;
} else {
cout << "Can't open database" << endl;
return 1;
}
C.disconnect ();
} catch (const std::exception &e) {
cerr << e.what() << std::endl;
return 1;
}
}
我的示例代码生成以下构建流。似乎与标准版本的 c++ 编译器存在兼容性问题。
/usr/bin/make -j16 -e -f Makefile
----------Building project:[ pgSample - Debug ]----------
clang: warning: -lpqxx: 'linker' input unused [-Wunused-command-line-argument]
clang: warning: -lpq: 'linker' input unused [-Wunused-command-line-argument]
/usr/bin/g++ -c "/Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp" -g -O0 -Wall -lpqxx -lpq -o Debug/main.cpp.o -I. -I.
clang: warning: -lpqxx: 'linker' input unused [-Wunused-command-line-argument]
clang: warning: -lpq: 'linker' input unused [-Wunused-command-line-argument]
In file included from /Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp:2:
In file included from /usr/local/include/pqxx/pqxx:2:
In file included from /usr/local/include/pqxx/array:4:
In file included from /usr/local/include/pqxx/array.hxx:17:
/usr/local/include/pqxx/internal/encoding_group.hxx:14:15: warning: nested namespace definition is a C++17 extension; define each namespace separately [-Wc++17-extensions]
namespace pqxx::internal
^~~~~~~~~~
{ namespace internal
/usr/local/include/pqxx/internal/encoding_group.hxx:18:6: warning: scoped enumerations are a C++11 extension [-Wc++11-extensions]
enum class encoding_group
^
/usr/local/include/pqxx/internal/encoding_group.hxx:53:3: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
std::size_t(char const buffer[], std::size_t buffer_len, std::size_t start);
^
In file included from /Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp:2:
In file included from /usr/local/include/pqxx/pqxx:2:
In file included from /usr/local/include/pqxx/array:4:
In file included from /usr/local/include/pqxx/array.hxx:18:
/usr/local/include/pqxx/internal/encodings.hxx:18:15: warning: nested namespace definition is a C++17 extension; define each namespace separately [-Wc++17-extensions]
namespace pqxx::internal
^~~~~~~~~~
{ namespace internal
/usr/local/include/pqxx/internal/encodings.hxx:58:3: warning: 'auto' type specifier is a C++11 extension [-Wc++11-extensions]
auto const scan{get_glyph_scanner(enc)};
^
/usr/local/include/pqxx/internal/encodings.hxx:58:14: error: declaration of variable 'scan' with deduced type 'const auto' requires an initializer
auto const scan{get_glyph_scanner(enc)};
^
/usr/local/include/pqxx/internal/encodings.hxx:58:18: error: expected ';' at end of declaration
auto const scan{get_glyph_scanner(enc)};
^
;
In file included from /Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp:2:
In file included from /usr/local/include/pqxx/pqxx:2:
In file included from /usr/local/include/pqxx/array:4:
/usr/local/include/pqxx/array.hxx:50:8: warning: scoped enumerations are a C++11 extension [-Wc++11-extensions]
enum class juncture
^
/usr/local/include/pqxx/array.hxx:82:32: warning: default member initializer for non-static data member is a C++11 extension [-Wc++11-extensions]
std::string::size_type m_pos = 0u;
^
/usr/local/include/pqxx/array.hxx:67:42: warning: use of enumeration in a nested name specifier is a C++11 extension [-Wc++11-extensions]
internal::encoding_group = internal::encoding_group::MONOBYTE);
^
In file included from /Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp:2:
In file included from /usr/local/include/pqxx/pqxx:3:
In file included from /usr/local/include/pqxx/binarystring:4:
In file included from /usr/local/include/pqxx/binarystring.hxx:21:
In file included from /usr/local/include/pqxx/result.hxx:23:
/usr/local/include/pqxx/except.hxx:89:11: error: exception specification of overriding function is more lax than base version
virtual ~sql_error() noexcept override;
^
/usr/local/include/pqxx/except.hxx:42:23: note: overridden virtual function is here
struct PQXX_LIBEXPORT failure : std::runtime_error
^
/usr/local/include/pqxx/except.hxx:89:23: error: expected ';' at end of declaration list
virtual ~sql_error() noexcept override;
^
;
/usr/local/include/pqxx/except.hxx:92:4: error: expected expression
[[nodiscard]] PQXX_PURE std::string const &query() const noexcept;
^
/usr/local/include/pqxx/except.hxx:92:17: error: expected member name or ';' after declaration specifiers
[[nodiscard]] PQXX_PURE std::string const &query() const noexcept;
^
/usr/local/include/pqxx/compiler-public.hxx:25:21: note: expanded from macro 'PQXX_PURE'
# define PQXX_PURE __attribute__((pure))
^
In file included from /Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp:2:
In file included from /usr/local/include/pqxx/pqxx:3:
In file included from /usr/local/include/pqxx/binarystring:4:
In file included from /usr/local/include/pqxx/binarystring.hxx:21:
In file included from /usr/local/include/pqxx/result.hxx:23:
/usr/local/include/pqxx/except.hxx:95:4: error: expected expression
[[nodiscard]] PQXX_PURE std::string const &sqlstate() const noexcept;
^
/usr/local/include/pqxx/except.hxx:95:17: error: expected member name or ';' after declaration specifiers
[[nodiscard]] PQXX_PURE std::string const &sqlstate() const noexcept;
^
/usr/local/include/pqxx/compiler-public.hxx:25:21: note: expanded from macro 'PQXX_PURE'
# define PQXX_PURE __attribute__((pure))
^
In file included from /Users/thomaspeters/Documents/Development/C-Simple-Projects/C-Simple-Projects/pgSample/main.cpp:2:
In file included from /usr/local/include/pqxx/pqxx:3:
In file included from /usr/local/include/pqxx/binarystring:4:
In file included from /usr/local/include/pqxx/binarystring.hxx:21:
In file included from /usr/local/include/pqxx/result.hxx:23:
/usr/local/include/pqxx/except.hxx:201:71: error: expected member name or ';' after declaration specifiers
explicit unexpected_rows(std::string const &msg) : range_error{msg} {}
^
/usr/local/include/pqxx/except.hxx:201:65: error: expected '('
explicit unexpected_rows(std::string const &msg) : range_error{msg} {}
^
/usr/local/include/pqxx/except.hxx:201:69: error: expected ';' after expression
explicit unexpected_rows(std::string const &msg) : range_error{msg} {}
^
;
/usr/local/include/pqxx/except.hxx:201:66: warning: expression result unused [-Wunused-value]
explicit unexpected_rows(std::string const &msg) : range_error{msg} {}
^~~
/usr/local/include/pqxx/except.hxx:212:3: error: expected member name or ';' after declaration specifiers
{}
^
/usr/local/include/pqxx/except.hxx:211:20: error: expected '('
sql_error{err, Q, sqlstate}
^
/usr/local/include/pqxx/except.hxx:211:21: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^~~
/usr/local/include/pqxx/except.hxx:211:26: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^
/usr/local/include/pqxx/except.hxx:211:37: error: expected ';' after expression
sql_error{err, Q, sqlstate}
^
;
/usr/local/include/pqxx/except.hxx:211:29: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^~~~~~~~
/usr/local/include/pqxx/except.hxx:222:3: error: expected member name or ';' after declaration specifiers
{}
^
/usr/local/include/pqxx/except.hxx:221:20: error: expected '('
sql_error{err, Q, sqlstate}
^
/usr/local/include/pqxx/except.hxx:221:21: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^~~
/usr/local/include/pqxx/except.hxx:221:26: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^
/usr/local/include/pqxx/except.hxx:221:37: error: expected ';' after expression
sql_error{err, Q, sqlstate}
^
;
/usr/local/include/pqxx/except.hxx:221:29: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^~~~~~~~
/usr/local/include/pqxx/except.hxx:231:3: error: expected member name or ';' after declaration specifiers
{}
^
/usr/local/include/pqxx/except.hxx:230:20: error: expected '('
sql_error{err, Q, sqlstate}
^
/usr/local/include/pqxx/except.hxx:230:21: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^~~
/usr/local/include/pqxx/except.hxx:230:26: warning: expression result unused [-Wunused-value]
sql_error{err, Q, sqlstate}
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
17 warnings and 20 errors generated.
make[1]: *** [Debug/main.cpp.o] Error 1
make: *** [All] Error 2
==== build ended with errors (20 errors, 46 warnings) ===
解决方案
刚刚学习，还有很长的路要走，但发现了一些链接器选项，可以使编译器的行为有所不同。我能够删除所有编译器警告、链接器警告，现在我的代码可以编译了。
使用：-std=cxx17
在 C++ 链接器选项中，这会导致编译器使用 cxx2017 标准。呃，仍然需要一些阅读。我可以理解它，但还不是很深刻。
托马斯
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