未定义的引用[仅限某些文件math.h＆QUOT;功能 [英] undefined reference to "only some math.h" functions

问题描述

我有一个奇怪的问题。

数学库已经被添加到我的makefile。

The math libraries has been added to my makefile.

# include standard C library
LDFLAGS += -lc
# include standard math library
LDFLAGS += -lm

和输出文件（.MAP）我可以看到，一切都已经正确链接：

and in the output file (.map) I can see that everything has been linked properly:

LOAD c:/gnu/powerpc-eabi/3pp.ronetix.powerpc-eabi/bin/../lib/gcc/powerpc-eabi/4.3.3/nof\libgcc.a
LOAD c:/gnu/powerpc-eabi/3pp.ronetix.powerpc-eabi/bin/../lib/gcc/powerpc-eabi/4.3.3/../../../../powerpc-eabi/lib/nof\libc.a
LOAD c:/gnu/powerpc-eabi/3pp.ronetix.powerpc-eabi/bin/../lib/gcc/powerpc-eabi/4.3.3/../../../../powerpc-eabi/lib/nof\libm.a

当我这样做

z = pow((double) 2, (double) 3);

它工作正常。但是，如果我测试另一个功能，如：

it works fine. But if I test another function like:

double result = asin(x);

I'll得到：

I´ll get:

undefined reference to `asin'
collect2: ld returned 1 exit status

怎么能这样呢？两者的 POW 和 ASIN 在提供的文件math.h ，见下图：

/* Non reentrant ANSI C functions.  */

#ifndef _REENT_ONLY
#ifndef __math_6881
extern double acos _PARAMS((double));
extern double asin _PARAMS((double));
extern double atan2 _PARAMS((double, double));
extern double cosh _PARAMS((double));
extern double sinh _PARAMS((double));
extern double exp _PARAMS((double));
extern double ldexp _PARAMS((double, int));
extern double log _PARAMS((double));
extern double log10 _PARAMS((double));
extern double pow _PARAMS((double, double));
extern double sqrt _PARAMS((double));
extern double fmod _PARAMS((double, double));
#endif /* ! defined (__math_68881) */
#endif /* ! defined (_REENT_ONLY) */

的怎么能工作，另一种生成链接的问题？的
如果我运行的 -nm 在 libm.a I'll得到以下结果：（抱歉巨大的输出，我只字复制部分的的罪的）

how can one work and the other one generate linker issue? If I run -nm on libm.a I´ll get the following result: (sorry for the huge output, I have only copied the sections with the word sin)

lib_a-e_asin.o:
         U __adddf3
         U __divdf3
         U __gtdf2
00000000 T __ieee754_asin
         U __ieee754_sqrt
         U __muldf3
         U __subdf3
         U fabs

lib_a-e_j0.o:
         U __adddf3
         U __divdf3
         U __gtdf2
00000470 T __ieee754_j0
         U __ieee754_log
         U __ieee754_sqrt
000009b8 T __ieee754_y0
         U __ltdf2
         U __muldf3
         U __subdf3
         U cos
         U fabs
000000b0 r pR2
00000108 r pR3
00000058 r pR5
00000000 r pR8
000000e0 r pS2
00000138 r pS3
00000088 r pS5
00000030 r pS8
00000004 t pzero
00000220 r qR2
00000280 r qR3
000001c0 r qR5
00000160 r qR8
00000250 r qS2
000002b0 r qS3
000001f0 r qS5
00000190 r qS8
00000218 t qzero
         U sin

lib_a-e_j1.o:
         U __adddf3
         U __divdf3
         U __gtdf2
00000470 T __ieee754_j1
         U __ieee754_log
         U __ieee754_sqrt
00000950 T __ieee754_y1
         U __muldf3
         U __subdf3
         U cos
         U fabs
00000004 t pone
000000b0 r pr2
00000108 r pr3
00000058 r pr5
00000000 r pr8
000000e0 r ps2
00000138 r ps3
00000088 r ps5
00000030 r ps8
00000218 t qone
00000220 r qr2
00000280 r qr3
000001c0 r qr5
00000160 r qr8
00000250 r qs2
000002b0 r qs3
000001f0 r qs5
00000190 r qs8
         U sin

lib_a-e_jn.o:
         U __adddf3
         U __divdf3
         U __floatsidf
         U __gedf2
         U __gtdf2
         U __ieee754_j0
         U __ieee754_j1
00000434 T __ieee754_jn
         U __ieee754_log
         U __ieee754_sqrt
         U __ieee754_y0
         U __ieee754_y1
00000000 T __ieee754_yn
         U __ltdf2
         U __muldf3
         U __subdf3
         U cos
         U fabs
         U sin


lib_a-e_sinh.o:
         U __adddf3
         U __divdf3
         U __gtdf2
         U __ieee754_exp
00000000 T __ieee754_sinh
         U __muldf3
         U __subdf3
         U expm1
         U fabs


lib_a-ef_asin.o:
         U __addsf3
         U __divsf3
         U __gtsf2
00000000 T __ieee754_asinf
         U __ieee754_sqrtf
         U __mulsf3
         U __subsf3
         U fabsf


lib_a-ef_j0.o:
         U __addsf3
         U __divsf3
         U __gtsf2
0000035c T __ieee754_j0f
         U __ieee754_logf
         U __ieee754_sqrtf
000006cc T __ieee754_y0f
         U __ltsf2
         U __mulsf3
         U __subsf3
         U cosf
         U fabsf
00000058 r pR2
00000084 r pR3
0000002c r pR5
00000000 r pR8
00000070 r pS2
0000009c r pS3
00000044 r pS5
00000018 r pS8
00000004 t pzerof
00000110 r qR2
00000140 r qR3
000000e0 r qR5
000000b0 r qR8
00000128 r qS2
00000158 r qS3
000000f8 r qS5
000000c8 r qS8
000001a0 t qzerof
         U sinf

lib_a-ef_j1.o:
         U __addsf3
         U __divsf3
         U __gtsf2
0000031c T __ieee754_j1f
         U __ieee754_logf
         U __ieee754_sqrtf
0000062c T __ieee754_y1f
         U __mulsf3
         U __subsf3
         U cosf
         U fabsf
00000004 t ponef
00000058 r pr2
00000084 r pr3
0000002c r pr5
00000000 r pr8
00000070 r ps2
0000009c r ps3
00000044 r ps5
00000018 r ps8
000001a0 t qonef
000000b0 r qr2
000000e0 r qr8
000000c8 r qs2
000000f8 r qs8
         U sinf

lib_a-ef_sinh.o:
         U __addsf3
         U __divsf3
         U __gtsf2
         U __ieee754_expf
00000000 T __ieee754_sinhf
         U __mulsf3
         U __subsf3
         U expm1f
         U fabsf

lib_a-er_lgamma.o:
         U __adddf3
         U __divdf3
         U __eqdf2
         U __fixdfsi
         U __floatsidf
00000004 T __ieee754_lgamma_r
         U __ieee754_log
         U __kernel_cos
         U __kernel_sin
         U __ltdf2
         U __muldf3
         U __nedf2
         U __subdf3
         U fabs
         U floor


lib_a-erf_lgamma.o:
         U __addsf3
         U __divsf3
         U __eqsf2
         U __fixsfsi
         U __floatsisf
00000004 T __ieee754_lgammaf_r
         U __ieee754_logf
         U __kernel_cosf
         U __kernel_sinf
         U __ltsf2
         U __mulsf3
         U __nesf2
         U __subsf3
         U fabsf
         U floorf

lib_a-k_sin.o:
         U __adddf3
         U __fixdfsi
00000000 T __kernel_sin
         U __muldf3
         U __subdf3

lib_a-kf_sin.o:
         U __addsf3
         U __fixsfsi
00000000 T __kernel_sinf
         U __mulsf3
         U __subsf3

lib_a-s_asinh.o:
         U __adddf3
         U __divdf3
         U __gtdf2
         U __ieee754_log
         U __ieee754_sqrt
         U __muldf3
00000000 T asinh
         U fabs
         U log1p

lib_a-s_cos.o:
         U __ieee754_rem_pio2
         U __kernel_cos
         U __kernel_sin
         U __subdf3
00000000 T cos

lib_a-s_isinf.o:
00000000 T isinf

lib_a-s_isinfd.o:
00000000 T __isinfd

lib_a-s_sin.o:
         U __ieee754_rem_pio2
         U __kernel_cos
         U __kernel_sin
         U __subdf3
00000000 T sin

lib_a-sf_asinh.o:
         U __addsf3
         U __divsf3
         U __gtsf2
         U __ieee754_logf
         U __ieee754_sqrtf
         U __mulsf3
00000000 T asinhf
         U fabsf
         U log1pf

lib_a-sf_cos.o:
         U __ieee754_rem_pio2f
         U __kernel_cosf
         U __kernel_sinf
         U __subsf3
00000000 T cosf

lib_a-sf_isinf.o:
00000000 T isinff

lib_a-sf_isinff.o:
00000000 T __isinff

lib_a-sf_sin.o:
         U __ieee754_rem_pio2f
         U __kernel_cosf
         U __kernel_sinf
         U __subsf3
00000000 T sinf

lib_a-w_asin.o:
         U __errno
         U __fdlib_version
         U __gtdf2
         U __ieee754_asin
         U __isnand
00000004 T asin
         U fabs
         U matherr
         U nan

lib_a-w_sincos.o:
         U cos
         U sin
00000000 T sincos

lib_a-w_sinh.o:
         U __errno
         U __fdlib_version
         U __gtdf2
         U __ieee754_sinh
         U finite
         U matherr
00000004 T sinh

lib_a-wf_asin.o:
         U __errno
         U __extendsfdf2
         U __fdlib_version
         U __gtsf2
         U __ieee754_asinf
         U __truncdfsf2
00000004 T asinf
         U fabsf
         U isnanf
         U matherr
         U nan

lib_a-wf_sincos.o:
         U cosf
00000000 T sincosf
         U sinf

lib_a-wf_sinh.o:
         U __errno
         U __extendsfdf2
         U __fdlib_version
         U __gtsf2
         U __ieee754_sinhf
         U __truncdfsf2
         U finitef
         U matherr
00000004 T sinhf

EDIT1：的
我测试了一些更多的问题如下（不是我原先上述）：

I tested some more and the problem is as follows (not what I originally stated above):

double aa;
double bb = 1.0;
double cc;
aa = sin(1.0);
cc = sin (bb);

什么时候我尝试建立情况是，我收到了未定义的引用的'在最后一行，这意味着当我使用常量它是好的，但是当我通过变量罪职能它不会链接。我还测试了其他许多数学函数和I'll得到完全相同的连接问题。当我传递一个变量到一个数学函数我不能链接了。任何想法？

What happens when I try to build is that I get a 'undefined reference' at the last line, meaning that when I use constants it is fine, but when I pass variables to the sin functions it will not link. I also tested many of the other math function and I´ll get the exact same linker issue. As soon as I pass a variable to a math function I can not link any more. any ideas?

推荐答案

连接器不是抱怨 POW（（双）2（双）3），因为编译器以恒定 8.0 替换它。你不应该依赖此行为;相反，你应该总是正确使用 -lm 选项。 （顺便说一句，这是更清楚地写成 POW（2.0,3.0）。

The linker isn't complaining about pow((double) 2, (double) 3) because the compiler is replacing it with a constant 8.0. You shouldn't depend on this behavior; instead, you should always use the -lm option properly. (BTW, that's more clearly written as pow(2.0, 3.0).

考虑下面的程序：

#include <stdio.h>
#include <math.h>
int main(void) {
    double x = 0.1;
    printf("%g\n", pow(2.0, 3.0));
    printf("%g\n", asin(x));
    return 0;
}

当我编译和链接使用它我的系统上

When I compile and link it on my system using

gcc c.c -o c

我得到：

/tmp/ccXx8ZRL.o: In function `main':
c.c:(.text+0x36): undefined reference to `asin'
collect2: ld returned 1 exit status

请注意，它抱怨 ASIN ，但不是关于 POW 。

Note that it complains about asin but not about pow.

如果我修改 POW 调用 POW（X，3.0），我得到：

If I change the pow call to pow(x, 3.0), I get:

/tmp/ccOeSaBK.o: In function `main':
c.c:(.text+0x24): undefined reference to `pow'
c.c:(.text+0x52): undefined reference to `asin'
collect2: ld returned 1 exit status

通常情况下，如果你要调用一个标准的数学库函数，你需要有的#include＆LT;文件math.h＆GT; 在源文件的顶部（I presume您已经有）的和的你需要在 -lm 选项传递给编译器的之后的文件需要它。 （链接器会跟踪尚未解决的引用，因此它需要看到，是指 ASIN 第一目标文件，因此它认为何时能解决这个问题数学库）。

Normally if you want to call a standard math library function, you need to have #include <math.h> at the top of the source file (I presume you already have that) and you need to pass the -lm option to the compiler after the file that needs it. (The linker keeps track of references that haven't been resolved yet, so it needs to see the object file that refers to asin first, so it can resolve it when it sees the math library.)

连接器不是抱怨调用 POW（2.0,3.0），因为GCC是足够聪明的它是一个常数 8.0 。有到战俘没有呼叫编译对象文件函数，因此链接器并不需要解决。如果我改变 POW（2.0,3.0）到 POW（X，3.0），编译器不知道是什么结果将是，所以它产生的呼叫

The linker isn't complaining about the call to pow(2.0, 3.0) because gcc is clever enough to resolve it to a constant 8.0. There's no call to the pow function in the compiled object file, so the linker doesn't need to resolve it. If I change pow(2.0, 3.0) to pow(x, 3.0), the compiler doesn't know what the result is going to be, so it generates the call.

这篇关于未定义的引用[仅限某些文件math.h＆QUOT;功能的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！