“&((char)b)”:居然犯了这样的低级错误

为了测试bool的底层存储,我写出了这样的代码:

bool b = 4;
char *pc = &((char)b); //My GODNESS!!
cout << int(*pc) << endl;

编译器给了我无情的拒绝:“''& requires l-value”。

看到这条消息,我真的有点儿不太相信这是我写出的代码(真的,我真不相信)!!居然犯了这样的低级错误,强制转换的结果不是左值,是不可以取地址的。所以我写到这里,给自己最强烈的警告。

改成下面这样就好了:
bool b = 4;
char *pc = (char*)(&b); //OK
cout << int(*pc) << endl;
 

/usr/bin/ld: /home/zwy/gitcode/snapShotServer/lib/lib_aws/libaws-cpp-sdk-core.a(ub_core.cpp.o): in function `Aws::Utils::Crypto::CRTHash::Update(unsigned char *, unsigned long)&#39;: ub_core.cpp:(.text+0xfa3): undefined reference to `Aws::Crt::ByteCursorFromArray(unsigned char const*, unsigned long)&#39; /usr/bin/ld: ub_core.cpp:(.text+0xfb8): undefined reference to `Aws::Crt::Crypto::Hash::Update(aws_byte_cursor const&amp;)&#39; /usr/bin/ld: /home/zwy/gitcode/snapShotServer/lib/lib_aws/libaws-cpp-sdk-core.a(ub_core.cpp.o): in function `Aws::Utils::Crypto::CRTSymmetricCipher::Good() co nst&#39;: ub_core.cpp:(.text+0xfed): undefined reference to `Aws::Crt::Crypto::SymmetricCipher::GetState() const&#39; /usr/bin/ld: /home/zwy/gitcode/snapShotServer/lib/lib_aws/libaws-cpp-sdk-core.a(ub_core.cpp.o): in function `void Aws::Crt::Variant&lt;std::__cxx11::basic_string &lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;, bool&gt;::VisitorUtil&lt;(short)0, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;ch ar&gt; &gt;, bool&gt;::VisitBinary&lt;Aws::Crt::Variant&lt;std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;, bool&gt;::CopyMoveConstructor&gt;(Aws:: Crt::Variant&lt;std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;, bool&gt;*, Aws::Crt::Variant&lt;std::__cxx11::basic_string&lt;char, std:: char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;, bool&gt; const&amp;, Aws::Crt::Variant&lt;std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;, bo ol&gt;::CopyMoveConstructor&amp;&amp;) [clone .isra.0] [clone .part.0]&#39;: ub_core.cpp:(.text+0x18ea): undefined reference to `aws_fatal_assert&#39; /usr/bin/ld: /home/zwy/gitcode/snapShotServer/lib/lib_aws/libaws-cpp-sdk-core.a(ub_core.cpp.o): in function `Aws::Utils::Crypto::CRTSecureRandomBytes::GetByte s(unsigned char*, unsigned long)&#39;: ub_core.cpp:(.text+0xb745): undefined reference to `Aws::Crt::ByteBufFromEmptyArray(unsigned char const*, unsigned long)&#39; /usr/bin/ld: ub_core.cpp:(.text+0xb750): undefined reference to `Aws::Crt::Crypto::GenerateRandomBytes(aws_byte_buf&amp;, unsigned long)&#39; /usr/bin/ld: /home/zwy/gitcode/snapShotServer/lib/lib_aws/libaws-cpp-sdk-core.a(ub_core.cpp.o): in function `Aws::Utils::Logging::s_aws_logger_redirect_log(aw s_logger*, aws_log_level, unsigned int, char const*, ...)&#39;: ub_core.cpp:(.text+0xc72f): undefined reference to `aws_log_subject_name&#39; /usr/bin/ld: /home/zwy/gitcode/snapShotServer/lib/lib_aws/libaws-cpp-sdk-core.a(ub_core.cpp.o): in function `Aws::Utils::Logging::ShutdownCRTLogging()&#39;: ub_core.cpp:(.text+0xcb5b): undefined reference to `aws_logger_get&#39; /usr/bin/ld: ub_core.cpp:(.text+0xcc33): undefined reference to `aws_logger_set&#39;
最新发布
06-14
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