[gcc r12-4002] [Ada] Document that gnatmem requires fixed-position executables

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:c4f826d933368a60087f9bcc72c798cf005a6636

commit r12-4002-gc4f826d933368a60087f9bcc72c798cf005a6636
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Wed Aug 4 15:07:17 2021 +0200

    [Ada] Document that gnatmem requires fixed-position executables
    
    gcc/ada/
    
            * doc/gnat_ugn/gnat_and_program_execution.rst (gnatmem): Document
            that it works only with fixed-position executables.

Diff:
---
 gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst b/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst
index c4f186ef130..24ef9d6ca41 100644
--- a/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst
+++ b/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst
@@ -3680,8 +3680,9 @@ execution of this erroneous program:
   The ``gnatmem`` utility monitors dynamic allocation and
   deallocation activity in a program, and displays information about
   incorrect deallocations and possible sources of memory leaks.
-  It is designed to work in association with a static runtime library
-  only and in this context provides three types of information:
+  It is designed to work for fixed-position executables in association
+  with a static runtime library only and in this context provides three
+  types of information:
 
   * General information concerning memory management, such as the total
     number of allocations and deallocations, the amount of allocated
@@ -3711,15 +3712,16 @@ execution of this erroneous program:
 
        $ gnatmem [ switches ] [ DEPTH ] user_program
 
-  The program must have been linked with the instrumented version of the
+  The user program must be linked with the instrumented version of the
   allocation and deallocation routines. This is done by linking with the
   :file:`libgmem.a` library. For correct symbolic backtrace information,
-  the user program should be compiled with debugging options
-  (see :ref:`Switches_for_gcc`). For example to build :file:`my_program`:
+  the user program should also both be compiled with debugging options
+  (see :ref:`Switches_for_gcc`) and be linked at a fixed position. For
+  example to build :file:`my_program` with ``gnatmake``:
 
     ::
 
-       $ gnatmake -g my_program -largs -lgmem
+       $ gnatmake -g my_program -largs -lgmem -no-pie
 
   As library :file:`libgmem.a` contains an alternate body for package
   ``System.Memory``, :file:`s-memory.adb` should not be compiled and linked