gdb fabs错误输出

https://sourceware.org/gdb/wiki/FAQ

GDB doesn't know the return type nor the type of the arguments for that function call, because there's no debug information available for it. Either provide debuginfo for the program or library which contains the function, or cast the function to a function pointer of the appropriate signature.

For example, to call fabs, which takes a double and returns a double, use:

(gdb) print ((double (*) (double)) fabs) ( -1.25 )

https://stackoverflow.com/questions/8570196/gdb-gives-strange-output-when-using-math-h-functions