What does the compiler error "missing binary operator before token" mean?
If you are on Linux, make sure that you do not have a header named features.h
inside your project files.
I had one with this name, which resulted in:
/usr/include/x86_64-linux-gnu/bits/huge_val.h:25: error: function pointer expected
or
/usr/include/bits/huge_val.h:26:18: error: missing binary operator before token "("
That is because some system headers like huge_val.h
use macros like __GNUC_PREREQ
that are defined by /usr/include/features.h
(learn more about this header in this SO question).
In my case I first saw this error when I started to use gcc's -I option which suddenly made gcc select my project include directory before the default system include directories.
You get this error sometimes if you have -fno-operator-names
in your compiler flags. I suffered from the exact error while building json
and this solved it.
This is not a compiler error, it is a preprocessor error. It occurs when the preprocessor encounters invalid syntax while trying to evaluate an expression in a #if
or #elif
directive.
One common cause is the sizeof
operator in an #if
directive:
For example:
#define NBITS (sizeof(TYPE)*8)
//later
#if (NBITS>16) //ERROR
This is an error because sizeof
is evaluated by the compiler, not the preprocesor.
Type casts are also not valid preprocessor syntax:
#define ALLBITS ((unsigned int) -1)
//later
#if (ALLBITS>0xFFFF) //ERROR
The rules for what can be in a valid expression are here.
Note also that #if
will evaluate an undefined macro as 0, unless it looks like it takes arguments, in which case you also get this error:
So if THIS
is undefined:
#if THIS == 0 //valid, true
#if THIS > 0 //valid, false
#if THIS() == 0 //invalid. ERROR
Typos in your #if
statement can also cause this message.