<span style="background-color:rgb(255,255,255);color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px">Hi all, </span><br><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">I notice in the mpich source code that Fortran string length arguments are supposed to be int. However, in many compilers this hidden argument is size_t. Below are excerpts from documentation of Intel ifort, GFortran and PathScale. (The last one claims to use int as the string length). In practice using an int here "just works" - at least for strings shorter than 2GB. Since the string length argument is passed by value there is little risk for any errors to occur as it is most likely to be passed in a register so any "additional upper bits" get cleared in the process of the call. Possibly it could be a problem with routines with vary many arguments where arguments are passed over the stack.</div>
<div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
./src/mpi/romio/adio/include/adio.h </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">./src/binding/f77/mpi_fortimpl.h </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">#ifdef USE_FORT_MIXED_STR_LEN </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
#define FORT_MIXED_LEN_DECL , int </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">#define FORT_END_LEN_DECL </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
#define FORT_MIXED_LEN(a) , int a </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">#define FORT_END_LEN(a) </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
#else </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">#define FORT_MIXED_LEN_DECL </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
#define FORT_END_LEN_DECL , int </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">#define FORT_MIXED_LEN(a) </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
#define FORT_END_LEN(a) , int a </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">#endif </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<b>Intel Fortran </b></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<a href="http://software.intel.com/sites/products/documentation/doclib/stdxe/2013/composerxe/compiler/fortran-win/index.htm" target="_blank" style="color:rgb(17,85,204)">http://software.intel.com/sites/products/documentation/doclib/stdxe/2013/composerxe/compiler/fortran-win/index.htm</a> </div>
<div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">(Not a perfect example, but the best I could find) I've seen more explicit formulations in earlier Intel manuals. </div>
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<a href="http://software.intel.com/en-us/forums/topic/270023" target="_blank" style="color:rgb(17,85,204)">http://software.intel.com/en-us/forums/topic/270023</a> </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
Is more to the point </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<b>GFortran </b></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<a href="http://www.xgear.eu/callfortranfromc.html" target="_blank" style="color:rgb(17,85,204)">http://www.xgear.eu/callfortranfromc.html</a> </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Fortran functions that receive string variables from C </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
C </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">This is slightly more complicated. The Fortran function must be declared at the beginning of the C calling function (e.g. main) like this: </div>
<div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"> extern void load_(char *string, size_t *len_string);</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Note that we have to pass all variables to Fortran as pointers. Our string variable is already a pointer, but we have to pass the string's length as a pointer too. Although the function name is not case sensitive in Fortran, it gains an underscore in the C declaration and when it is called: </div>
<div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"> len_string = strlen(string); </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"> load_(string, &len_string);</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
Note that in passing the string from C to Fortran we also need to pass the length of the string, hence the use of strlen beforehand (not forgetting to declare the string length variable as a size_trather than an int). </div>
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<div>[<i> NOTE: </i>The above is likely incorrect in that I believe the declaration should be size_t len_string and the call load_(string, len_string).</div><div>The actual arguments are passed by reference but the hidden length arguments are likely passed by value.</div>
<div> (My comment)</div><div>]</div><div><br></div></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<b>Pathscale </b></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><b><br></b></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<a href="http://www.pathscale.com/EKOPath-User-Guide#htoc66" target="_blank" style="color:rgb(17,85,204)">http://www.pathscale.com/EKOPath-User-Guide#htoc66</a> </div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Like most Fortran compilers, we represent character strings passed to subprograms with a character pointer, and add an integer length parameter to the end of the call list. </div>