我已经在 Mac OS X 10.7.5(自制 GCC)上测试了 GCC 4.7.1,以及提供的系统/usr/bin/gcc
和/usr/bin/clang
,它们都产生了与您报告的结果相同的结果。
我同意您的分析,即当复数float
的两个项都表示为整数时,必须进行转换。double
C 2011 标准包括以下示例:
ISO/IEC 9899:2011 §6.7.9 初始化
¶24 示例 1 如果<complex.h>
已经#include
d,则声明
int i = 3.5;
double complex c = 5 + 3 * I;
用值 3 定义和初始化 i,用值 5. 0 + i3 初始化 c。0。
这清楚地表明您应该能够编写整数表达式并获得有效的double complex
(尽管示例是非规范性的)。float
但是,它没有解决在转换为之前是否应将整数值转换为double
,但语言中没有其他地方可以自动执行此操作(显然,您可以强制它),因此不太可能是预期的解释。
总的来说,我认为这很可能是一个可以报告给 GCC 团队的错误(这不是我提倡的轻率行为)。如果您运行gcc --help
,则输出以以下消息结尾:
For bug reporting instructions, please see:
<http://gcc.gnu.org/bugs.html>
我将扩展您的示例,如下所示(或者,我确实扩展了您的示例,如下所示):
#include <stdio.h>
#include <complex.h>
int main(void)
{
double complex test1, test2, test3, test4, test5, test6, test7, test8;
test1 = 81141117.0;
test2 = 81141117.0 + I * 0;
test3 = 81141117 + I * 0.0;
test4 = 81141117 + I * 0;
test5 = (float)81141117 + I * 0;
test6 = 81141117 + I * (float)0;
test7 = 81141117.F + I * 0;
test8 = 81141117 + I * 0.F;
printf("%ld + %ld I, %ld + %ld I\n", (long)creal(test1), (long)cimag(test1), (long)creal(test2), (long)cimag(test2));
printf("%ld + %ld I, %ld + %ld I\n", (long)creal(test3), (long)cimag(test3), (long)creal(test4), (long)cimag(test4));
printf("%ld + %ld I, %ld + %ld I\n", (long)creal(test5), (long)cimag(test5), (long)creal(test6), (long)cimag(test6));
printf("%ld + %ld I, %ld + %ld I\n", (long)creal(test7), (long)cimag(test7), (long)creal(test8), (long)cimag(test8));
}
我得到的输出是:
81141117 + 0 I, 81141117 + 0 I
81141117 + 0 I, 81141120 + 0 I
81141120 + 0 I, 81141120 + 0 I
81141120 + 0 I, 81141120 + 0 I
如您所见,最后两行有显式(float)
强制转换或显式浮点常量,产生的结果与有问题的行相同(但值是合法的)。
您可能(或可能不)想尝试使用CMPLX
, CMPLXF
(也可能是CMPLXL
)宏;如果它们为某些“有趣”的定义产生了“有趣”的值,我只会将它们添加到报告的示例中。
编译器版本号:
$ /usr/gcc/v4.7.1/bin/gcc --version
gcc (GCC) 4.7.1
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ /usr/bin/gcc --version
i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ clang --version
Apple clang version 4.1 (tags/Apple/clang-421.11.65) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin11.4.2
Thread model: posix
$