Fix too late initialization of tasking runtime with standalone library

[Eric Botcazou]

The Tasking_Runtime_Initialize routine installs the tasking version of the 
RTS_Lock manipulation routines and thus needs to be called very early before 
the elaboration of all the Ada units of the program, including those of the 
runtime itself.

This is guaranteed by the binder when the tasking runtime is explicitly 
dragged into the link.  However, for a standalone dynamic library that does 
not depend on the tasking runtime and is auto-initialized, no such guarantee 
holds, even though the library might be later dragged into a link that 
contains the tasking runtime.

This change causes the routine to be called even earlier, in particular at 
load time when a (standalone) dynamic library is involved in the link, so as 
to meet the requirements.  It will cause the routine to be called twice if the 
main subprogram is generated by the binder, but this is harmless since the 
routine is idempotent.

Tested on x86-64/Linux, applied on the mainline (branches are not affected).


2025-03-27  Eric Botcazou  <ebotca...@adacore.com>

ada/
            * libgnarl/s-tasini.adb (Tasking_Runtime_Initialize): Add pragma
            Linker_Constructor for the procedure.

-- 
Eric Botcazou
diff --git a/gcc/ada/libgnarl/s-tasini.adb b/gcc/ada/libgnarl/s-tasini.adb
index 144ac7c1c4e..ae0826590c8 100644
--- a/gcc/ada/libgnarl/s-tasini.adb
+++ b/gcc/ada/libgnarl/s-tasini.adb
@@ -115,11 +115,13 @@ package body System.Tasking.Initialization is
    procedure Tasking_Runtime_Initialize;
    pragma Export (Ada, Tasking_Runtime_Initialize,
                   "__gnat_tasking_runtime_initialize");
+   pragma Linker_Constructor (Tasking_Runtime_Initialize);
    --  This procedure starts the initialization of the GNARL. It installs the
-   --  tasking versions of the RTS_Lock manipulation routines. It is called
+   --  tasking version of the RTS_Lock manipulation routines. It is called
    --  very early before the elaboration of all the Ada units of the program,
    --  including those of the runtime, because this elaboration may require
-   --  the initialization of RTS_Lock objects.
+   --  the initialization of RTS_Lock objects, which means that it must only
+   --  contain code to which pragma Restrictions (No_Elaboration_Code) applies.
 
    --------------------------
    -- Change_Base_Priority --