在64位上4GB之后的bad_alloc [英] bad_alloc after 4GB on 64bit
问题描述
大家好，为什么这会失败引发bad_alloc
int * v = new int [6000000000];
如果成功
int * v =（int *）malloc（（unsigned）6000000000）
在同一台机器上，相同的编译器g ++，64bit linux red hat
enterprise 4，没有用户的ulimits，足够的虚拟内存ecc ...
在这两种情况下使用
g ++ source.cpp -o executable编译
文件总是一个c ++ .cpp文件，上面那行是唯一一个
不同的文件。
谢谢
Hi guys, why does this fail raising bad_alloc
int *v = new int [6000000000];
if this succeeds
int *v = (int *) malloc((unsigned)6000000000)
both on the same machine, same compiler g++, 64bit linux red hat
enterprise 4, no ulimits on the user, enough virtual memory ecc...
in both cases compiled with
g++ source.cpp -o executable
the file is always a c++ .cpp file, that line above is the only one that
differs.
Thanks
推荐答案
cman写道：
cman wrote:
大家好，为什么这会失败提高bad_alloc
int * v = new int [6000000000];
Hi guys, why does this fail raising bad_alloc
int *v = new int [6000000000];
AFAIK，任何整数文字都将被解释为32位有符号整数，即使编译器是64位编译器也是如此。我认为这对于32位编译器来说是向后兼容的原因。如果你想要一个64位的int literal的int literal，你必须在后面添加LL：6000000000LL应该
这样做。
AFAIK, any integer literal will be interpreted as 32 bit signed integer, even
though the compiler is a 64bit compiler. I think that this is meant to be so for
backward compatibility reasons to 32bit compilers. If you want an int literal to
be a 64bit int literal, you''ll have to add LL at the back: 6000000000LL should
do the trick.
如果成功
int * v =（int *）malloc（（unsigned）6000000000）
都在同一台机器上，同样的编译器g ++，64bit linux red hat
enterprise 4，没有用户的ulimits，足够的虚拟内存ecc ...
在这两种情况下使用
g ++ source.cpp -o可执行文件来源
该文件始终是一个c ++ .cpp文件，上面的那一行是唯一一个
不同。
if this succeeds
int *v = (int *) malloc((unsigned)6000000000)
both on the same machine, same compiler g++, 64bit linux red hat
enterprise 4, no ulimits on the user, enough virtual memory ecc...
in both cases compiled with
g++ source.cpp -o executable
the file is always a c++ .cpp file, that line above is the only one that
differs.
问候，
Stuart
Regards,
Stuart
int * v = new int [6000000000 ];
请求24000000000字节。
int *v = new int [6000000000];
Request for 24000000000 bytes.
int * v =（int *）malloc（（unsigned）6000000000）
int *v = (int *) malloc((unsigned)6000000000)
请求6000000000字节。
Leo Havm？ller。
Request for 6000000000 bytes.
Leo Havm?ller.
int * v = new int [6000000000];
int *v = new int [6000000000];
>
请求24000000000字节。
>
Request for 24000000000 bytes.
所以int是4个字节？
So an int is 4 bytes?
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