Re: Controlling the linking of shared libraries

[anon@att.net]

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For a package: 
  Files: libtest.adb, libtest.ads

  gnat make libtest.adb -o libtest.so -cargs -fPIC -largs -shared

For seperate files: 
  Files: test1.adb, test2.adb

  gnat compile test1.adb  -cagrs -fPIC
  gnat make    test2.adb  -o libtest.so  -cargs -fPIC -largs -shared test1.o



All shared source code must be compiled with "-fPIC' option and be linked 
using "-sharded". And should have ".so" as part of the file.

You could compile as "-o libtest.so.xxx" and then link this file to name
"libtest.so"

The "-cargs" sets gcc compiler options 
The "-bargs" sets gcc binder options 
The "-largs" sets gcc linker options 


In <992cqbFm9mU1@mid.individual.net>, =?UTF-8?B?QmrDtnJu?= Persson <bjorn@xn--rombobjrn-67a.se> writes:
>I'll try to explain my problem in more detail and see if that makes it clear 
>what I need.
>
>First, please note that I'm not talking about compiling a program and 
>linking it to a shared library. I'm talking about compiling the shared 
>library itself. When you build a shared library there is a linking phase 
>where you take all the .o files you just compiled and combine them into a 
>..so file (or a .dll file if you're in Windows land, but I'm in GNU land 
>here). I want to pass some options to the linker to control some details in 
>how it generates the .so file.
>
>Second, I'm writing this with my Fedora packager hat on. Packagers take 
>programs and libraries that others have written and compile them into Fedora 
>packages that the Fedora project distributes. Ideally we should be able to 
>do this without modifying the upstream source code. Rather than writing 
>custom patches for each and every package, we want to define a common set of 
>command line parameters and/or environment variables that control how 
>packages are built. In practice we often have to patch the upstream 
>projects' build systems, as they arent written to be flexible enough, but 
>the less we have to patch, and the more we can control the build with 
>command line parameters and environment variables, the better.
>
>The Fedora project recently decided to start using a linker option called 
>"relro" in all packages as a security measure. This means that we need to 
>pass the command line parameter "-Wl,-z,relro" to gcc so that gcc will in 
>turn pass "-z relro" to ld. This parameter is not to be used in the 
>compilation phase, only in the linking phase when gcc is invoked as a linker 
>driver. This was the first distribution-wide linker option that was defined 
>in Fedora. Previously the common set of parameters contained only compiler 
>options, used in the compilation phase.
>
>Now, some projects are built using makefiles and let the makefile handle the 
>linking phase by invoking gcc directly. Those cases are not what I'm 
>concerned over right now. Other projects have Gnat project files that 
>control the whole build process, and in those cases I need to find a way to 
>make Gnatmake or GPRbuild pass "-Wl,-z,relro" to gcc in the linking phase. I 
>tried using "-largs -Wl,-z,relro" for this, and found that it has the 
>desired effect when the project being built is a program. It does however 
>not have any noticeable effect when the project being built is a shared 
>library.
>
>According to the manual the attribute Library_Options can be used in project 
>files to specify linker options, but as I explained above patching each and 
>every project file is undesirable. Therefore I came here to ask you guys: 
>Does anyone know how to pass command line parameters to Gnatmake and 
>GPRbuild that they should forward to gcc when they invoke gcc as a linker 
>driver to build a shared library, given that -largs is not the answer? A 
>solution using environment variables might also be preferable to patching.
>
>-- 
>Björn Persson
>PGP key A88682FD