未定义对nlopt _...符号的引用

Question

我对Fortran还是很陌生，这听起来像是一个愚蠢的问题。在编译作为示例发布在NLOPT Wiki中的Fortran代码时，我遇到错误。

我使用以下命令在Ubuntu 18.04 LTS中进行编译：

gfortran example-nlopt.f90 -o example-nlopt -I/usr/local/include/

在终端中产生以下错误：

/tmp/ccbAim6b.o: In function `MAIN__':
example-nlopt.f90:(.text+0x26): undefined reference to `nlo_create_'
example-nlopt.f90:(.text+0x42): undefined reference to `nlo_get_lower_bounds_'
example-nlopt.f90:(.text+0x67): undefined reference to `nlo_set_lower_bounds_'
example-nlopt.f90:(.text+0x8a): undefined reference to `nlo_set_min_objective_'
example-nlopt.f90:(.text+0xca): undefined reference to `nlo_add_inequality_constraint_'
example-nlopt.f90:(.text+0x10e): undefined reference to `nlo_add_inequality_constraint_'
example-nlopt.f90:(.text+0x12d): undefined reference to `nlo_set_xtol_rel_'
example-nlopt.f90:(.text+0x164): undefined reference to `nlo_optimize_'
example-nlopt.f90:(.text+0x305): undefined reference to `nlo_destroy_'
collect2: error: ld returned 1 exit status

Answer 1

根据我在nlopt文档（https://nlopt.readthedocs.io/en/latest/NLopt_Installation/#changing-the-installation-directory中看到的内容）看来，您只需要指定要链接的库即可。也许试试这个：

gfortran  -I/usr/local/include/ -L/usr/local/lib example-nlopt.f90 -o example-nlopt -lnlopt -lm

这假定您在/ usr / local / lib中有libnlopt.so，如果没有，则使用-L选项指向它的位置。