Now let's imagine we pick Microsoft compiler. I'd suggest to perform an MT build and link it dynamically with MSVCRT.DLL. Idea is to use MSVCRT primarily for BIO and other strictly internal purposes (keep in mind that MSCVRT.DLL can be redistributed). At the same time I'd sanitize functions appearing in "grep 'FILE \*' include/openssl/*" and replace calls to stdio with wrappers, which would treat FILE * as opaque pointer. Idea is to link these wrappers to corresponding stdio functions provided by compiler environment at run-time. How? We could require user application to be linked with a module of own design, which exports a symbol, and then we could refer to this symbol from DllMain in libeay32.dll for the purposes of linking the wrappers with vendor stdio. For example. Supplied code to be compiled and linked with user application could look as following (this is just an example!):
static void *link_table[]={stdin,stout,stderr,fprintf,fread,fclose}; void ** __declspec(dllexport) get_link_table() { return link_table; }
While DllMain in libeay32.dll could:
h=GetModuleHandle(NULL);//.exe image used to create the calling process proc=GetProcAddress(h,"get_link_table"); if (proc==NULL) report_or_log_error_and_exit(); tbl=(*proc)(); // use tbl to feed the wrappers
It should be enough to simply add the supplied module to the target project to make magic happen and work with any run-time environment or flag combination. There is a minor problem with Borland, which insists on different function name decoration and uses different .LIB format, but it seems that it can be easily resolved with IMPLIB... Thoughts? A.
I like it! :-)
Three comments:
* Do we really need to have the "get_link_table" function? I think
we should be able to import just the link table itself
* We can define the link table in a header file and have the user
simply include the header file in only one place OR provide a
#define prior to the #include to define the link table in only one
place
* The link table should contain a table format version number so
that in case we need to grow the table in the future it will be
possible to do so and produce the appropriate compatibility errors.- Jeff
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