From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Buck To: greened@eecs.umich.edu Cc: egcs@cygnus.com Subject: Re: Template Instantiation Date: Sun, 08 Feb 1998 18:44:00 -0000 Message-id: <199802090242.SAA05477@atrus.synopsys.com> References: X-SW-Source: 1998-02/msg00335.html > Can someone clarify exactly how template instantiation > works in egcs? I'm using x86/Linux/ELF and SPARC/Solaris > systems. On both of these systems, it works pretty much like it does with Borland C++. All needed templates are instantiated in each object file, but weak symbols are used. At link time, one weak symbol is used as the definition. If you have a recent GNU ld, the duplicate definitions, if any, get stripped out and are not included in the binary. If you have an older linker or are using the Solaris linker, everything works, but your executable may contain extra copies of some functions. > I've been using -frepo when linking object files. When creating > liraries, I've been manually instantiating templates though IIRC, > someone mentioned that this wasn't necessary. You're better off using no flags at all and just allowing things to work. > In the (very outdated) g++ FAQ at www.cygnus.com, It contains text referring to old versions as well as sections referring to the latest version. > I found this passage: > > Jason Merrill writes: "To perform closure on a set of objects, just try > to link them together. It will fail, but as a side effect all needed > instances will be generated in the objects." > > Maybe I'm dense, but I don't understand this. It refers to 2.7.2.x . The procedure is not recommended with 2.8.0 or egcs. The reason it worked is because -frepo attaches the instantiated functions to the original .o files. So if you did g++ -frepo *.o -o dummy then -frepo would try to instantiate templates as needed; the link will fail because there is no main defined. But after that you can do ar qc libfoo.a *.o to make the library, and the library will contain template expansions.