本文介绍了ld:对符号'log2 @@ GLIBC_2.2.5'的未定义引用的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
for (level = 1; level <= log2((double)size); level++)
^
好像使用log2()一样，但是怎么了?我实际上将它与OpenMPI代码一起使用，但是注释此行可以解决问题.
Seems like its from using log2() but whats wrong? I am using it with OpenMPI code actually, but commenting this line fixes things.
完整源代码( http://pastie .org/7559178 )，请参见第40行
Full Source(http://pastie.org/7559178) see line 40
[jiewmeng@JM Assign3]$ mpicc -o cpi cpi.c && mpirun -np 16 cpi
/usr/bin/ld: /tmp/cca9x4he.o: undefined reference to symbol 'log2@@GLIBC_2.2.5'
/usr/bin/ld: note: 'log2@@GLIBC_2.2.5' is defined in DSO /usr/lib/libm.so.6 so try adding it to the linker command line
/usr/lib/libm.so.6: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status
似乎像log2(4)一样可以工作，但是我不能传递变量?
Seems like log2(4) will work but I cant pass in a variable?
推荐答案
为了链接libm，您需要添加-lm自变量，作为此文档； 数学部门在Linux下的MPI 说:
In in order to link libm you need to add -lm argument, as this document; MPI under Linux in the Math Department says:
mpicc -o sample sample.c -lm
mpicc -o sample sample.c -lm
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