Re: How to supply O/S linker arguments with gprbuild?

["Björn Lundin" <b.f.lundin@gmail.com>]

Den 2020-06-22 kl. 17:51, skrev Warren:
> I have a GNAT project that has these pragma statements embedded to get the sucker to link. However, the directory is only valid for an instance on my Mac, so I need a better solution to replace:
> 
>     pragma Linker_Options("-L/usr/local/Cellar/readline/8.0.4/lib");
>     pragma Linker_Options("-lreadline");
> 
> I've tried to find the solution in the gnat documents but they seem to fall short of what I need to do (could not find an example nor direction in this -- perhaps I missed it).
> 
> My project file looks something like this:
> 
> project MyProject is
>      for Languages use ("ada", "c");
>      for Source_Dirs use ("src");
>      for Object_Dir use "obj";
>      for Main use ("main.adb");
> end MyProject;
> 
> I've tried a variety of gpr things, but unsuccessfully.
> 
> Warren
> 

This was just (basically) discussed recently in thread
'Checking for OS in gnatstudio project file(.gpr)'

I replied with scnenario/environment variables does the trick

db_libs := ();
case db is
   when Oracle     => db_libs := db_lib1;
   when Postgresql => db_libs := db_lib2;
   when sqlserver  => db_libs := db_lib3;
end case

then you can use  db_libs and fill it up and use it like



ORACLE_HOME   := external ("ORACLE_HOME", "ORACLE_HOME_not_set");
ORACLE_CLIENT := external ("ORACLE_CLIENT", "ORACLE_CLIENT_not_set");
ORA_INST      := external ("ORACLE_INST", "ORACLE_INST_not_set");
LIB_SATTMATE  := external ("SATTMATE_A",  "SATTMATE_A_not_set");
....

there is also
   Target_Machine : Environment.OS_Version_Type := Environment.Os_Version;

   Compiler_Version : Environment.Compiler_Version_Type := 
Environment.Compiler_Version;

  Data_Base : Environment.Database_Type := Environment.Database;

then it comes down to casing the correct combinations

case Target_Machine is
   when "AIX_7.1"      =>
     case Database is
        when "oracle_11" => db_libs :=
                (SMT & "/global/sqlifc_oracle.o",
                ORACLE_CLIENT & "/lib/libclntsh.a");

        when "oci"       => Data_Base_Libs :=
                (ORACLE_CLIENT & "/lib/libclntsh.a",
                 SATTMATE_OCILIB & "/lib/libocilib.a");
        when others => null;
     end case;

     Platform_Dependent_Compiler_Switches := ("-mminimal-toc") ;
     Platform_Dependent_Linker_Switches := ("-L" & SMT & "/global",
     LIB_SATTMATE,
     "-Xlinker",
     "-bhalt:5") &  db_libs;


  when "windows_6.2"  =>
    case Database is
      when "oracle_11" => db_libs :=
        (SMT & "/global/sqlifc_oracle.o",
         ORA_INST & "/precomp/lib/oraSQL11.LIB");
      when "oci"       => db_libs :=
         ("-L" & ORACLE_CLIENT & "/bin",
         "-loci",
         "-L" & SATTMATE_OCILIB,
         "-lociliba");
      when "sqlserver" => db_libs := ("-lodbc32");
      when others => null;
    end case;

    Platform_Dependent_Compiler_Switches := ("-gnatP");
    Platform_Dependent_Linker_Switches :=
    ("-L" & SMT & "/global",
    "-lsattmate") & db_libs;

  when "linux-x64"    => ....
  when "linux-arm32"  => ...

end case;


then use it like (the not previously shown varibles get values in other 
case statemets)

  package Compiler is
    for Default_Switches ("Ada") use
          Platform_Independent_Compiler_Switches &
          Compiler_Dependent_Compiler_Switches &
          Platform_Dependent_Compiler_Switches;
  end Compiler;


package Linker is
   for Default_Switches ("Ada") use Platform_Dependent_Linker_Switches;
end Linker;


Scenario variables are useful too to include a certain directory among 
sources or not, like having common specs but os/db depedent bodies.
make directories win_x86, winx64,Linux_x64/mac/aix/whaterever and 
include the correct one in Sources_dir


for Source_Dirs use common_dirs & (../win_x86);


-- 
Björn