要求malloc从malloc返回吗？ [英] is typecasting return from malloc required?
问题描述
为什么我会收到以下错误？我是否需要明确地将malloc返回的
指针强制转换为char *？
谢谢，
ceo
[root @ lin1 tmp] #cat malloc.cpp
#include< stdio.h>
#include< malloc.h> ;
#include< string.h>
int main（）{
char * s = NULL;
s = malloc（sizeof（char）* 10）;
strcpy（s，blah blah）;
printf（ \ n％s \ n，s）;
返回0;
}
[root @ lin1 tmp] #gcc malloc.cpp
malloc.cpp：在函数`int main（）''：
malloc.cpp：8：无法转换`void *'分配给'char *''
[root @ lin1 tmp] #gcc -v
从/ usr / lib / gcc-lib / i386-redhat读取规范-linux / 2.96 / specs
gcc版本2.96 20000731（Red Hat Linux 7.2 2.96-108.1）
[root @ lin1 tmp]＃
ceo写道：
为什么我会收到以下错误？我是否需要明确地将malloc返回的指针强制转换为char *？
谢谢，
[root @ lin1 tmp] #cat malloc.cpp
#include< stdio.h>
#include< malloc.h>
#include< string.h>
int main（ ）{
char * s = NULL;
s = malloc（sizeof（char）* 10）;
strcpy（s，blah blah）;
printf（" \ n％s \ n"，s）;
返回0;
}
[root @ lin1 tmp] #gcc malloc.cpp < broc> malloc.cpp：在函数`int main（）''中：
malloc.cpp：8：在赋值时无法将`void *''转换为`char *''
[root @ lin1 tmp] #gcc -v
从/usr/lib/gcc-lib/i386-redhat-linux/2.96/specs阅读规范
gcc版本2.96 20000731（Red Hat Linux 7.2 2.96-108.1）
[root @ lin1 tmp]＃
提示：哪个头文件是malloc声明的？
>提示：哪个头文件是malloc声明的？
你好akarl，
如果我包含stdlib.h，那么
i会得到同样的错误这就是你的意思。
谢谢，
ceo
[root @ lin1 tmp] #cat malloc .cpp
#include< stdio.h>
#include< stdlib.h>
#include< string.h>
int main（）{
char * s = NULL;
s = malloc（sizeof（char） * 10）;
strcpy（s，blah blah）;
printf（" \ n％s \ n"，s）;
返回0;
}
[root @ lin1 tmp] #gcc malloc.cpp
malloc .cpp：在函数`int main（）''中：
malloc.cpp：8：在赋值时无法将`void *''转换为`char *''
[root @ lin1 tmp] #gcc -v
从/usr/lib/gcc-lib/i386-redhat-linux/2.96/specs阅读规格
gcc版本2.96 20000731（Red Hat Linux 7.2 2.96-108.1）
[root @ lin1 tmp]＃
因为它是作为C ++代码编译的。
如果更改文件名 ; malloc.cpp" tomalloc.c，
添加类型转换操作符，或者
使用new []操作符，可以避免该错误。
但是如果用gcc编译C ++代码（如果你尝试第二个或第三个）或者
" cc"命令
您将收到链接错误。为避免此错误，您应该使用
" g ++"进行编译。或者c ++
谢谢，
Norihiro Kamae在日本
ceo写道：
为什么我会收到以下错误？我是否需要明确地将malloc返回的指针强制转换为char *？
谢谢，
[root @ lin1 tmp] #cat malloc.cpp
#include< stdio.h>
#include< malloc.h>
#include< string.h>
int main（ ）{
char * s = NULL;
s = malloc（sizeof（char）* 10）;
strcpy（s，blah blah）;
printf（" \ n％s \ n"，s）;
返回0;
}
[root @ lin1 tmp] #gcc malloc.cpp < broc> malloc.cpp：在函数`int main（）''中：
malloc.cpp：8：在赋值时无法将`void *''转换为`char *''
[root @ lin1 tmp] #gcc -v
从/usr/lib/gcc-lib/i386-redhat-linux/2.96/specs阅读规范
gcc版本2.96 20000731（Red Hat Linux 7.2 2.96-108.1）
[root @ lin1 tmp]＃
hi,
why do i get the following error? do i need to explicitly typecast the
pointer returned by malloc to char *?
thanks,
ceo
[root@lin1 tmp]# cat malloc.cpp
#include <stdio.h>
#include <malloc.h>
#include <string.h>
int main() {
char *s = NULL;
s = malloc(sizeof( char) * 10);
strcpy(s, "blah blah");
printf("\n%s\n", s);
return 0;
}
[root@lin1 tmp]# gcc malloc.cpp
malloc.cpp: In function `int main ()'':
malloc.cpp:8: cannot convert `void *'' to `char *'' in assignment
[root@lin1 tmp]# gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-108.1)
[root@lin1 tmp]#
ceo wrote:hi,
why do i get the following error? do i need to explicitly typecast the
pointer returned by malloc to char *?
thanks,
ceo
[root@lin1 tmp]# cat malloc.cpp
#include <stdio.h>
#include <malloc.h>
#include <string.h>
int main() {
char *s = NULL;
s = malloc(sizeof( char) * 10);
strcpy(s, "blah blah");
printf("\n%s\n", s);
return 0;
}
[root@lin1 tmp]# gcc malloc.cpp
malloc.cpp: In function `int main ()'':
malloc.cpp:8: cannot convert `void *'' to `char *'' in assignment
[root@lin1 tmp]# gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-108.1)
[root@lin1 tmp]#
Hint: In which header file is malloc declared?
> Hint: In which header file is malloc declared?
hello akarl,
i get the same error if i include stdlib.h if that''s what you meant.
thanks,
ceo
[root@lin1 tmp]# cat malloc.cpp
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
char *s = NULL;
s = malloc(sizeof( char) * 10);
strcpy(s, "blah blah");
printf("\n%s\n", s);
return 0;
}
[root@lin1 tmp]# gcc malloc.cpp
malloc.cpp: In function `int main ()'':
malloc.cpp:8: cannot convert `void *'' to `char *'' in assignment
[root@lin1 tmp]# gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-108.1)
[root@lin1 tmp]#
Because it was compiled as an C++ code.
If you change the file name "malloc.cpp" to "malloc.c",
add typecast operator, or
use new[] operator, you can avoid that error.
But if you compile C++ code (if you try 2nd or 3rd one) with "gcc" or
"cc" command
you will get a link error. To avoid this error you should compile with
"g++" or "c++"
thanks,
Norihiro Kamae in Japan
ceo wrote:
hi,
why do i get the following error? do i need to explicitly typecast the
pointer returned by malloc to char *?
thanks,
ceo
[root@lin1 tmp]# cat malloc.cpp
#include <stdio.h>
#include <malloc.h>
#include <string.h>
int main() {
char *s = NULL;
s = malloc(sizeof( char) * 10);
strcpy(s, "blah blah");
printf("\n%s\n", s);
return 0;
}
[root@lin1 tmp]# gcc malloc.cpp
malloc.cpp: In function `int main ()'':
malloc.cpp:8: cannot convert `void *'' to `char *'' in assignment
[root@lin1 tmp]# gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-108.1)
[root@lin1 tmp]#
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