题
以下代码是否错误，或者Mac上的 header 存在问题？该错误未在Linux上出现，这使我得出结论，它不是错误的代码，尽管在Linux上成功编译并不是对ISO遵从性进行特别严格的测试。
源代码(MCVE)
#include <stdio.h>
#include <complex.h>
void foo(const double *A, int *size){
for(int i=0;i < size[0]; ++i){
for(int j=0;j < size[1]; ++j){
printf("(%.2e,%.2e) ", creal(A[i + j * size[0]]), cimag(A[i + j * size[0]]));
}
}
}
苹果
系统信息
$ uname -a
Darwin redacted 15.4.0 Darwin Kernel Version 15.4.0: Fri Feb 26 22:08:05 PST 2016; root:xnu-3248.40.184~3/RELEASE_X86_64 x86_64
英特尔编译器
$ icpc -v
icpc version 16.0.2 (gcc version 4.9.0 compatibility)
$ icpc -c ttc-creal.cpp
ttc-creal.cpp(7): error: identifier "creal" is undefined
printf("(%.2e,%.2e) ", creal(A[i + j * size[0]]), cimag(A[i + j * size[0]]));
^
ttc-creal.cpp(7): error: identifier "cimag" is undefined
printf("(%.2e,%.2e) ", creal(A[i + j * size[0]]), cimag(A[i + j * size[0]]));
^
compilation aborted for ttc-creal.cpp (code 2)
LLVM编译器
$ clang++ -v
Apple LLVM version 7.3.0 (clang-703.0.29)
Target: x86_64-apple-darwin15.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
$ clang++ -c ttc-creal.cpp
ttc-creal.cpp:7:33: error: use of undeclared identifier 'creal'
printf("(%.2e,%.2e) ", creal(A[i + j * size[0]]), cimag(A[i + j * size[0]]));
^
ttc-creal.cpp:7:60: error: use of undeclared identifier 'cimag'
printf("(%.2e,%.2e) ", creal(A[i + j * size[0]]), cimag(A[i + j * size[0]]));
^
2 errors generated.
的Linux
系统信息
$ uname -a
Linux redacted 2.6.32-573.18.1.el6.centos.plus.x86_64 #1 SMP Wed Feb 10 18:09:24 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
GNU编译器
$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/gcc/5.3.0/libexec/gcc/x86_64-unknown-linux-gnu/5.3.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /home/redacted/Work/GCC/gcc-5.3.0/configure --prefix=/opt/gcc/5.3.0 --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --enable-languages=c,c++,fortran --with-tune=native --enable-bootstrap --enable-lto --with-mpfr --with-isl --with-gmp --with-mpc --with-cloog --enable-gold --enable-ld --disable-multilib
Thread model: posix
gcc version 5.3.0 (GCC)
$ g++ -c ttc-creal.cpp
<no error>
英特尔编译器
$ icpc -v
icpc version 17.0.0 Beta (gcc version 5.3.0 compatibility)
$ icpc -c ttc-creal.cpp
<no error>
LLVM编译器
$ clang++ -v
clang version 3.4.2 (tags/RELEASE_34/dot2-final)
Target: x86_64-redhat-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/4.4.4
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.7
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/4.4.7
$ clang++ -c ttc-creal.cpp
<no error>
调查中
我已经阅读了Mac上所有相关的
complex.h，ccomplex和complex header ，但看不到出现此问题的明显原因。 最佳答案
这只是Clang对C++标准的阅读-参见that answer-在我看来，这是正确的。基本上，您不应该在C++中使用C99复杂类型和关联函数，而应该使用std::complex<T>。两种复杂类型都应与布局兼容，并且您应该能够在C和C++代码之间传递复杂数据。g++的complex.h包括<ccomplex>(在C++ 11模式下)和C <complex.h>，因此该代码使用GCC(在我的情况下为Homebrew)进行编译。我没有用于OS X的英特尔编译器，但是您可以检查icpc -E ttc-creal.cpp | grep complex的功能，并观察包含文件扩展的顺序。
铛:
$ clang++ -E ttc-creal.cpp | grep "^# 1 " | grep complex
# 1 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/complex.h" 1 3
# 1 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/ccomplex" 1 3
# 1 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/complex" 1 3
GCC:
$ g++-5 -E ttc-creal.cpp | grep "^# 1 " | grep complex
# 1 "/usr/local/Cellar/gcc/5.3.0/include/c++/5.3.0/complex.h" 1 3
# 1 "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/complex.h" 1 3 4
$ g++-5 -std=c++11 -E ttc-creal.cpp | grep "^# 1 " | grep complex
# 1 "/usr/local/Cellar/gcc/5.3.0/include/c++/5.3.0/complex.h" 1 3
# 1 "/usr/local/Cellar/gcc/5.3.0/include/c++/5.3.0/ccomplex" 1 3
# 1 "/usr/local/Cellar/gcc/5.3.0/include/c++/5.3.0/complex" 1 3
# 1 "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/complex.h" 1 3 4
您可以通过以下方式强制Clang包含
<path to SDK>/usr/include/complex.h:#include "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/complex.h"
并且您的MCVE可以编译，但是这样做可能是一个非常糟糕的主意(tm)。
顺便说一下，在带有Clang 3.4.1(错误)和GCC 4.8.5(成功)的FreeBSD 10.2-RELEASE上观察到了相同的行为。
所有功劳归功于Potatoswatter-顶部引用答案的作者。
关于c++ - 标识符 “creal”未定义-在Mac上可见，但在Linux上不可见，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/36747506/