In xcode when including cmath get error: '::acos' has not been declared, etc

I get the following errors when trying to build a small and simple project that includes <cmath> in Xcode:

cmath: '*' has not been declared

'::acos' has not been declared

In file included from /Xcode4/Projects/libraryLAFMath/Classes/libraryLAFMath.cp

In file included from /Xcode4/Projects/libraryLAFMath/Classes/libraryLAFMath.h

'::acos' has not been declared in /Xcode4/Platforms/开发者_如何学CiPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.1.sdk/usr/include/c++/4.2.1/cmath

...

The error log complains about all the other math functions as well, sin, pow, etc, not just acos. I looked inside cmath source code and it references the globally defined corresponding math functions from math.h, ie ::acos etc. Since the root error complains about the non-existance of ::acos one would assume that math.h can't be found, but a) it exists, and b) I'd get a different error complaining that math.h can't be found.

The source code is as follows:

libraryLAFMath.cp:

#include "libraryLAFMath.h"

libraryLAFMath.h:

#include <cmath>
struct libraryLAFMath {
    void test() {
        double a = std::acos(0);
    }
};

Now, I have another project from an outside source that uses cmath and compiles fine. I tried comparing build settings between these two projects but they are pretty much the same. I am using LLVM GCC 4.2 compiler, but get similar result when using GCC 4.2, so it's not a compiler settings issue I believe.

I'm new to Xcode development and any help is appreciated.

There is a file I have in my project named Math.h with a capital M, and it seems the compiler gets confused and tries to include Math.h instead of math.h.

I posted this answer on an alternate thread on the topic, but thought it worth including here as well:

I had this problem - it was driving me crazy but I tracked down the cause, and it was a little different than what I've seen reported on this issue.

In this case, the general cmath header (or math.h - the error and solution occur in C++ or C) had architectural environment switches to include architecture specific math subheaders. The architecture switch (environment variable) hadn't been defined, so it was punting and not actually including the headers that truly defined the math functions.

So there was indeed a single math.h or cmath.h, and it was included, but that wasn't enough to get the math functions. In my case, rather than define the architectural variable, I instead found the location of the correct sub math headers and added them to my compile path. Then the project worked!

This seems to be an issue that comes up a lot when porting Linux projects to OS-X. I'd imagine it might occur anytime a project was moved betwee platforms such that the standard library headers are arranged differently.