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.NET Forum / Languages / Managed C++ / June 2007The static library benefits
Hello, In VS2005, if APP A is using a static library B.lib, although there are many objects contained in the B.lib, but App only use part of it, will the compiler only adopted the part that the App actually need, or bind all the objects of B.lib into the App? App A --> B.lib > Hello, > In VS2005, if APP A is using a static library B.lib, although there [quoted text clipped - 3 lines] > > App A --> B.lib Later, I test it in the VS App A --> B.lib --> C.lib Then I call C.lib function in App A, it works. It approve that, B.lib contain all the method of C.lib. But Whether App A contain all the method of B and C.lib is unknown. > In VS2005, if APP A is using a static library B.lib, although there > are many objects contained in the B.lib, but App only use part of it, > will the compiler only adopted the part that the App actually need, or > bind all the objects of B.lib into the App? Only the used part is contained in the final application. (it also depends how the lib is organized in modules).  SignatureMihai Nita [Microsoft MVP, Windows - SDK] http://www.mihai-nita.net ------------------------------------------ Replace _year_ with _ to get the real email > > In VS2005, if APP A is using a static library B.lib, although there > > are many objects contained in the B.lib, but App only use part of it, [quoted text clipped - 8 lines] > ------------------------------------------ > Replace _year_ with _ to get the real email The B.lib will include all the functions of C.lib, even there are no app use B.lib. Right? >>> In VS2005, if APP A is using a static library B.lib, although there >>> are many objects contained in the B.lib, but App only use part of it, [quoted text clipped - 10 lines] > The B.lib will include all the functions of C.lib, even there are no > app use B.lib. Right? Sealo: No. A .lib file is not linked. It is just a collection of .obj files. If your A.exe references B.lib, abd B.lib references C.lib, then all the .obj files of B.lib and C.lib will be available to the A.exe linker. Only those that are actually used will be retained in the image. SignatureDavid Wilkinson Visual C++ MVP >>>> In VS2005, if APP A is using a static library B.lib, although there >>>> are many objects contained in the B.lib, but App only use part of it, [quoted text clipped - 14 lines] > > No. A .lib file is not linked. It is just a collection of .obj files. If That's why it wouldn't contain only the functions of C needed by B. If you pass C.lib to the lib command building B.lib, then C.lib will be included in its entirety. > your A.exe references B.lib, abd B.lib references C.lib, then all the .obj > files of B.lib and C.lib will be available to the A.exe linker. Only those > that are actually used will be retained in the image. > "David Wilkinson" <no-reply@effisols.com> wrote in message >> No. A .lib file is not linked. It is just a collection of .obj files. If [quoted text clipped - 6 lines] >> files of B.lib and C.lib will be available to the A.exe linker. Only those >> that are actually used will be retained in the image. Hi Ben: Oh yes, I misread sealo's post. He didn't say that B.lib would contain only the stuff from C.lib that it needed; somehow I thought he did. SignatureDavid Wilkinson Visual C++ MVP >>>> In VS2005, if APP A is using a static library B.lib, although there >>>> are many objects contained in the B.lib, but App only use part of [quoted text clipped - 18 lines] > linker. Only those that are actually used will be retained in the > image. One more detail - the linker normally can only choose to load a module (an .obj file) or not from a library - so if that module contains 20 functions and only 1 is referenced, all 20 will still be present in the linked image. But, there's a compiler switch - /Gy ("separate functions for linker") which will put each and every function into it's own section, allowing the linker to include only those functions that are actually used. Compiling with /Gy will make your .obj's and .lib's larger and will increase link time, but will normally decrease final image size. -cd > One more detail - the linker normally can only choose to load a module (an > .obj file) or not from a library - so if that module contains 20 functions [quoted text clipped - 4 lines] > will make your .obj's and .lib's larger and will increase link time, but > will normally decrease final image size. Hi Carl: I didn't know that. I thought that by default the linker would whittle away at the image so that nothing not needed was present. Another thing learned. SignatureDavid Wilkinson Visual C++ MVP >> One more detail - the linker normally can only choose to load a module >> (an .obj file) or not from a library - so if that module contains 20 [quoted text clipped - 10 lines] > I didn't know that. I thought that by default the linker would whittle > away at the image so that nothing not needed was present. But the linker might not have the information on which global variables and helper functions are used by which public functions... > Another thing learned. > "David Wilkinson" <no-reply@effisols.com> wrote in message >> Hi Carl: [quoted text clipped - 4 lines] > But the linker might not have the information on which global variables and > helper functions are used by which public functions... Hi Ben: Mmmm. The linker will sure complain if anything is missing, so why can't it keep a list of things it has found not to be missing? I dig myself a little deeper ... SignatureDavid Wilkinson Visual C++ MVP >> "David Wilkinson" <no-reply@effisols.com> wrote in message >>> Hi Carl: [quoted text clipped - 9 lines] > Mmmm. The linker will sure complain if anything is missing, so why can't > it keep a list of things it has found not to be missing? oops, I meant to say file-scoped variables and helper functions.... which would be resolved by the compiler and not appear in the link symbols. > I dig myself a little deeper ...
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