C++ fmtlib："Undefined reference" 构建和#include <> 这个库后出错

Question

我从 https://github.com/fmtlib/fmt and then executed the following commands from official documentation https://fmt.dev/latest/usage.html 下载了库：

mkdir build
cd build
cmake ..
sudo make install

命令执行无误。 sudo make install命令的最终输出：

Install the project...
-- Install configuration: "Release"
-- Installing: /usr/local/lib/libfmt.a
-- Installing: /usr/local/include/fmt/args.h
-- Installing: /usr/local/include/fmt/chrono.h
-- Installing: /usr/local/include/fmt/color.h
-- Installing: /usr/local/include/fmt/compile.h
-- Installing: /usr/local/include/fmt/core.h
-- Installing: /usr/local/include/fmt/format.h
-- Installing: /usr/local/include/fmt/format-inl.h
-- Installing: /usr/local/include/fmt/locale.h
-- Installing: /usr/local/include/fmt/os.h
-- Installing: /usr/local/include/fmt/ostream.h
-- Installing: /usr/local/include/fmt/printf.h
-- Installing: /usr/local/include/fmt/ranges.h
-- Installing: /usr/local/include/fmt/xchar.h
-- Installing: /usr/local/lib/cmake/fmt/fmt-config.cmake
-- Installing: /usr/local/lib/cmake/fmt/fmt-config-version.cmake
-- Installing: /usr/local/lib/cmake/fmt/fmt-targets.cmake
-- Installing: /usr/local/lib/cmake/fmt/fmt-targets-release.cmake
-- Installing: /usr/local/lib/pkgconfig/fmt.pc

接下来我创建了包含以下内容的文件 main.cpp：

#include <fmt/core.h>

int main()
{
    fmt::print("Hello");

    return 0;
}

并用命令g++ main.cpp -o main编译了它。但是，编译结果出现以下错误：

/usr/bin/ld: /tmp/ccJ3FzHH.o: in the function «main»:
main.cpp:(.text+0x8a): undefined reference to «fmt::v8::vprint(fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<fmt::v8::appender, char> >)»
collect2: error: ld returned 1 exit status

我正在使用 Ubuntu 20.04

Answer 1

在编译命令中添加参数-lfmt可以解决问题。 -l<name> 参数通常代表将库 <name> 包含到编译中（参见 GCC documentation）

命令如下所示：

$ g++ main.cpp -lfmt -o main

C++ fmtlib："Undefined reference" 构建和#include <> 这个库后出错

C++ fmtlib: "Undefined reference" error after building and #include <> this library

c++

include

fmt