Mex Error on Linux - redefinition of typedef

I am trying to compile a mex file to interact with a C function in Matlab. My C function contains various typedefs that appear to conflict with Matlab definitions. When I run:

mex myMxFxn.c sourceFxn.c

I get several messages like this:

/jc/myCode/ft1/my_types.h:11: error: redefinition of typedef 'int8_T'
/usr2/matlab/matlab2017a/extern/include/tmwtypes.h:203: note: previous declaration of 'int8_T' was here
/jc/myCode/ft1/my_types.h:12: error: redefinition of typedef 'uint8_T'
/usr2/matlab/matlab2017a/extern/include/tmwtypes.h:218: note: previous declaration of 'uint8_T' was here
(etc...)

My definitions (in my_types.h) are:

typedef signed char int8_T;
typedef unsigned char uint8_T;
etc...

The definitions in tmwtypes.h are as follows:

typedef INT8_T int8_T;
typedef UINT8_T uint8_T;
(etc...)

If I remove my typedefs my C function falls apart. Seems like Matlab and my C code are both heavily dependent on their respective definitions of those types. How can I prevent the conflict (ideally without changing all my C type names)?

Answer 1

[Himanshu]

Hey,

I had also faced this issue in older versions of MATLAB; this seems to be a bug ithat was fixed in the version R2018b. So I am assuming you were using a version older than that.

The conflict arises from the redefinition of typedefs in your custom header file my_types.h and MATLAB's tmwtypes.h. You can resolve this issue by conditionally including your typedefs only when they are not already defined by MATLAB.

Modify your my_types.h file to conditionally define these types only if they haven't been defined yet. You can use preprocessor directives to check if a type is already defined:cCopy code#ifndef INT8_T, as shown in the code snippet below.

#ifndef INT8_T
typedef signed char int8_T;
#endif
#ifndef UINT8_T
typedef unsigned char uint8_T;
#endif

Hope this helps!