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从boost::绑定1和2占位符运行make失败。。。?

boost c++

patrick · 技术社区 · 2 年前

我正在尝试运行make来构建一个项目,我得到了:

In file included from validation.cpp:46:
In file included from /opt/homebrew/opt/boost/include/boost/math/distributions/poisson.hpp:40:
In file included from /opt/homebrew/opt/boost/include/boost/math/special_functions/gamma.hpp:17:
In file included from /opt/homebrew/opt/boost/include/boost/math/tools/series.hpp:16:
/opt/homebrew/opt/boost/include/boost/math/tools/config.hpp:23:6: warning: "The minimum language standard to use Boost.Math will be C++14 starting in July 2023 (Boost 1.82 release)" [-W#warnings]
#    warning "The minimum language standard to use Boost.Math will be C++14 starting in July 2023 (Boost 1.82 release)"
     ^
validation.cpp:173:111: error: use of undeclared identifier '_1'
        pool.NotifyEntryRemoved.connect(boost::bind(&MemPoolConflictRemovalTracker::NotifyEntryRemoved, this, _1, _2));
                                                                                                              ^
validation.cpp:173:115: error: use of undeclared identifier '_2'
        pool.NotifyEntryRemoved.connect(boost::bind(&MemPoolConflictRemovalTracker::NotifyEntryRemoved, this, _1, _2));
                                                                                                                  ^
validation.cpp:183:114: error: use of undeclared identifier '_1'
        pool.NotifyEntryRemoved.disconnect(boost::bind(&MemPoolConflictRemovalTracker::NotifyEntryRemoved, this, _1, _2));
                                                                                                                 ^
validation.cpp:183:118: error: use of undeclared identifier '_2'
        pool.NotifyEntryRemoved.disconnect(boost::bind(&MemPoolConflictRemovalTracker::NotifyEntryRemoved, this, _1, _2));
                                                                                                                     ^
1 warning and 4 errors generated.
make[2]: *** [libbitcoin_server_a-validation.o] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all-recursive] Error 1

编译器为什么抱怨 _1 和 _2 ?

我在以下位置阅读了故障排除文档: https://www.boost.org/doc/libs/1_64_0/libs/bind/doc/html/bind.html#bind.troubleshooting.msvc_specific_using_boost_bind

但我看不到任何关于这个问题的信息,也看不到如何解决它。

1 回复 | 直到 2 年前

sehe 2 年前

为什么编译器抱怨_1和_2?

你没有显示你的代码。然而,消息引用了以下几行:

pool.NotifyEntryRemoved.connect(boost::bind(&MemPoolConflictRemovalTracker::NotifyEntryRemoved, this, _1, _2));
pool.NotifyEntryRemoved.disconnect(boost::bind(&MemPoolConflictRemovalTracker::NotifyEntryRemoved, this, _1, _2));

现在,自从 _1 和 _2 没有找到,你知道它缺少资格 boost::placeholders::_1 或类似的using指令

using namespace boost::placeholders;

请注意,在(非常!)旧版本的Boost中,占位符只在全局命名空间中。对于包括即将发布的1.83.0版本在内的一长系列版本,如果包含旧版标题,仍然会警告此更改

#include <boost/bind.hpp>

而不是新位置:

#include <boost/bind/bind.hpp>

您将看到以下警告:

BOOST_PRAGMA_MESSAGE(
  "The practice of declaring the Bind placeholders (_1, _2, ...) "
  "in the global namespace is deprecated. Please use "
  "<boost/bind/bind.hpp> + using namespace boost::placeholders, "
  "or define BOOST_BIND_GLOBAL_PLACEHOLDERS to retain the current behavior."
)

正如你所看到的,这给了你 另一种 补救措施,我不会推荐。显然,您正在使用的库将它们的实现切换到了名称空间更干净的版本,并且您的代码默默地依赖于不推荐使用的全局占位符。