[英]C++ error: expected primary-expression before ‘.’ token
I looked at the earlier questions but still i was not satisfied, hence i am posting this. 我看了之前的问题,但仍然不满意,因此我发布了这个。 I was trying to compile the C++ code written by someone else. 我试图编译其他人编写的C ++代码。
/*
file1.h
*/
#include <stdio.h>
#include <stdlib.h>
typedef struct
{
struct
{
unsigned member1;
unsigned member2;
} str1;
struct
{
unsigned member3;
unsigned member4;
} str2;
struct
{
unsigned member5;
unsigned member6;
} str3;
} CONFIG_T;
/*
file1.c
*/
CONFIG_T cfg =
{
.str1 = { 0x01, 0x02 },
.str2 = { 0x03, 0x04 },
.str3 = { 0x05, 0x06 }
};
Compiled with std C++11 and i get below error. 用std C ++ 11编译,我得到以下错误。 Why the '.' 为什么 '。' has been used in code while assigning values ? 在分配值时是否已在代码中使用?
home $$ g++ -c -std=gnu++0x initialze_list.cpp
initialze_list.cpp:34: error: expected primary-expression before ‘.’ token
initialze_list.cpp:35: error: expected primary-expression before ‘.’ token
initialze_list.cpp:36: error: expected primary-expression before ‘.’ token
I was not able to understand the reason for error. 我无法理解错误的原因。 Please help. 请帮忙。
What you posted is C code, not C++ code (note the .c file extention). 您发布的是C代码,而不是C ++代码(请注意.c文件扩展名)。 However, the following code: 但是,以下代码:
CONFIG_T cfg =
{
{ 0x01, 0x02 },
{ 0x03, 0x04 },
{ 0x05, 0x06 }
};
should work fine. 应该工作正常。
You can also read about C++11 initialize lists in the wiki . 您还可以阅读Wiki中的C ++ 11初始化列表。
Designated aggregate initializers is a C99 feature, ie it is a feature of C language. 指定的聚合初始化器是C99特性,即它是C语言的一个特性。 It is not present in C++. 它不存在于C ++中。
If you insist on compiling it as C++, you'll have to rewrite the initialization of cfg
. 如果你坚持将它编译为C ++,你将不得不重写cfg
的初始化。
/*
file1.c
*/
CONFIG_T cfg =
{
.str1 = { 0x01, 0x02 },
.str2 = { 0x03, 0x04 },
.str3 = { 0x05, 0x06 }
};
That code is using a C99 feature called designated initializers . 该代码使用称为指定初始化程序的C99功能。 As you have observed, that feature is not available in C++ and C++11. 正如您所观察到的,C ++和C ++ 11中没有该功能。
As suggested in this answer you should use a C compiler for C code. 如本回答所示,您应该使用C编译器来代码。 You can still link it to your C++ application. 您仍然可以将它链接到您的C ++应用程序。 You could use cmake
to do the build configuration for you. 您可以使用cmake
为您执行构建配置。 A simple example: 一个简单的例子:
/* f1.h */
#ifndef MYHEADER
#define MYHEADER
typedef struct { int i, j; } test_t;
extern test_t t;
#endif
/* f1.c */
#include "f1.h"
test_t t = { .i = 5, .j = 6 };
/* f0.cc */
extern "C" { #include "f1.h" }
#include <iostream>
int main() {
std::cout << t.i << " " << t.j << std::endl;
}
# CMakeLists.txt
add_executable(my_executable f0.cc f1.c)
just run mkdir build; cd build; cmake ..; make
只需运行mkdir build; cd build; cmake ..; make
mkdir build; cd build; cmake ..; make
mkdir build; cd build; cmake ..; make
from your source directory. mkdir build; cd build; cmake ..; make
您的源目录。
Thanks to all ... 谢谢大家 ...
After all the analysis i found that the above code has C99 feature called 经过所有分析后我发现上面的代码都有C99功能调用
Designated initializer . 指定的初始化程序 。
To compile this code in C++ i have changed the code to normal initialization as below. 要在C ++中编译此代码,我已将代码更改为正常初始化,如下所示。
========================== ==========================
/*
* initialze_list.cpp
*/
#include <stdio.h>
typedef struct
{
struct
{ unsigned member1;
unsigned member2;
} str1;
struct
{ unsigned member3;
unsigned member4;
} str2;
struct
{ unsigned member5;
unsigned member6;
} str3;
} CONFIG_T;
CONFIG_T cfg =
{
{ 0x01, 0x02 },
{ 0x03, 0x04 },
{ 0x05, 0x06 }
};
/* End of file */
================================== ==================================
This code compiled properly without the error in C++. 这段代码编译正确,没有C ++中的错误。
$$ g++ -c initialze_list.cpp $$ g ++ -c initialze_list.cpp
$$ g++ -c -std=gnu++0x initialze_list.cpp $$ g ++ -c -std = gnu ++ 0x initialze_list.cpp
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