OpenSSL compilation errors in Windows

Nagalakshmi V J nagalakshmi.j at
Tue Oct 1 05:41:46 UTC 2019

Hi Sergio,

We are using OpenSSL APIs in our product code. We are not making any changes in OpenSSL. Our product code is a C++ code and it makes use of openSSL APIs for some functionality.

This compilation error we are getting in Linux and windows platforms. But in Linux, we have a '-fpermissive' flag which is suppressing those errors as warnings and so compilation is getting successful.

The issue here is in Windows , we are not able to find alternative flag for -'fpermissive' in Visual studio and due to that compilation is unsuccessful. It would be helpful if anyone suggests some option to get the compilation successful.

Thanks and regards,

From: Sergio NNX <sfhacker at>
Sent: Monday, September 30, 2019 9:06 PM
To: Dr. Matthias St. Pierre <Matthias.St.Pierre at>; Nagalakshmi V J <nagalakshmi.j at>; Michael Mueller <abaci.mjm at>
Cc: openssl-users at; Umamaheswari Nagarajan <umamaheswari.nagarajan at>
Subject: Re: OpenSSL compilation errors in Windows

** This mail has been sent from an external source **


I haven't had a chance to compile the exact OpenSSL version using g++ compiler as stated by the user/poster.

If this user is using a modified or altered version of OpenSSL provided source code, is there support available? Don't get me wrong, I don't mind helping out but .....

I'll try to compile OpenSSL source code this evening and I'll post my findings here.



From: openssl-users <openssl-users-bounces at<mailto:openssl-users-bounces at>> on behalf of Dr. Matthias St. Pierre <Matthias.St.Pierre at<mailto:Matthias.St.Pierre at>>
Sent: Tuesday, 1 October 2019 12:28 AM
To: Nagalakshmi V J <nagalakshmi.j at<mailto:nagalakshmi.j at>>; Michael Mueller <abaci.mjm at<mailto:abaci.mjm at>>
Cc: openssl-users at<mailto:openssl-users at> <openssl-users at<mailto:openssl-users at>>; Umamaheswari Nagarajan <umamaheswari.nagarajan at<mailto:umamaheswari.nagarajan at>>
Subject: AW: OpenSSL compilation errors in Windows

> OpenSSL code is compiling without any issues. When it is used from our product code and while compiling using C++ compiler, the issue is seen.

As I wrote previously, the error you posted was caused  by the fact that you are compiling Ansi C (a.k.a ISO/IEC 9899:1990, a.k.a C90) source code

using a C++ compiler. While C permits a cast from 'void *' to 'anytype *', C++ doesn't allow it without an explicit cast.

Only the *public* OpenSSL headers are guaranteed to be includable by a C++ compiler (they contain the necessary ` extern "C" ` blocks, etc.),

not the internal headers. Including *internal* headers is neither supported nor possible with a C++ compiler. And as Matt Caswell already told you,

there are no compatibility guarantees for those headers.


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