<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">To take two lines from your example, you could do something like this if you don’t want to re-write Boost.Logging or build/use native Swift facilities to write to logs:<div class=""><br class=""></div><div class="">BoostLog.h:<span class="Apple-tab-span" style="white-space:pre"> </span>// Use this to bridge to Swift via C-compatibility</div><div class=""><br class=""></div><div class="">extern “C” void logTrace(const char * str);</div><div class="">extern “C” void logDebug(const char * str);</div><div class=""><br class=""></div><div class="">BoostLog.cpp:<span class="Apple-tab-span" style="white-space:pre"> </span>// this is the implementation</div><div class=""><br class=""></div><div class="">#include “BoostLog.h”</div><div class="">#include <boost/log/trivial.hpp></div><div class="">#include <string></div><div class=""><br class=""></div><div class="">void logTrace(const char* str)</div><div class="">{</div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>BOOST_LOG_TRIVIAL(trace) << std::string(str);</div><div class="">}</div><div class=""><br class=""></div><div class=""><div class="">void logDebug(const char* str)</div><div class="">{</div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>BOOST_LOG_TRIVIAL(debug) << std::string(str);</div><div class="">}</div><div class=""><br class=""><div><blockquote type="cite" class=""></blockquote></div></div><div class=""><br class=""></div><div class="">You would then use logTrace and logDebug within Swift like any other C-functions(using the appropriate Swift<->C interoperability conventions). How you package it up to include in your Swift project is another whole subject.</div><div class=""><br class=""></div><div class="">This is the general scheme by which you would include C++ into Swift (or any other language other than Obj-C++, for that matter, as Jens as noted previously).</div><div class=""><br class=""></div><div class="">Jonathan</div><div class=""><br class=""></div><div><blockquote type="cite" class=""><div class="">On Jan 13, 2017, at 12:37 PM, Ethin Probst via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">So you don't know how I could directly port this to Swift--or make an</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">indirect port?</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">On 1/13/17, Jens Alfke <</span><a href="mailto:jens@mooseyard.com" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">jens@mooseyard.com</a><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">> wrote:</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class=""><br class=""><blockquote type="cite" class="">On Jan 13, 2017, at 8:18 AM, Ethin Probst via swift-users<br class=""><<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote<br class=""><br class="">I was wondering how I could go about using the Boost library project<br class="">(among others) in swift?<br class=""></blockquote><br class="">No, it’s generally not feasible to use C++ libraries from any other<br class="">language. The main reasons are that (a) name-mangling of C++ functions means<br class="">that there’s no reliable way to tell the other language the name of the<br class="">function you want to call, and (b) C++ has so many language features that<br class="">are tightly entwined with the way you call functions — constructors,<br class="">copying, assignment, references, implicit conversions, operator overloading,<br class="">etc.<br class=""><br class="">In the simple example you gave there are several warning signs:<br class="">* BOOST_LOG_TRIVIAL etc. appear to be macros since they’re in all caps. Who<br class="">knows what functions they actually call?<br class="">* The “<<“ operator expands [unmangles] to some complex function name which<br class="">is very compiler-dependent.<br class="">* It’s very probable that the “<<“ operator is defined as an inline<br class="">function, so it may not even appear in the binary of the compiled Boost<br class="">library at all.<br class="">* The C string constants on the right hand side are probably being<br class="">implicitly converted to C++ std::strings before the call. Or maybe not. And<br class="">the conversion likely happens on the caller’s side, i.e. the compiler has to<br class="">know to create a std::string before calling and then destruct it<br class="">afterwards.<br class=""><br class="">The only practical way to call a C++ API from another language is to write<br class="">glue code, a set of functions that call the library, but which have a plain<br class="">C API and use only C types. Pretty much any language has a way to call C<br class="">functions, so you can now call the C API which will call the C++ code.<br class=""><br class="">—Jens<br class=""></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">--<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Signed,</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Ethin D. Probst</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">swift-users mailing list</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="mailto:swift-users@swift.org" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">swift-users@swift.org</a><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="https://lists.swift.org/mailman/listinfo/swift-users" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">https://lists.swift.org/mailman/listinfo/swift-users</a></div></blockquote></div><br class=""></div></body></html>