[Ada] Fix PR ada/99264

[Eric Botcazou]

This fixes the build breakage introduced by the latest glibc release.

Tested on x86-64/Linux, applied on mainline, 10 and 9 branches.


2021-03-05  Eric Botcazou  <ebotca...@adacore.com>

        PR ada/99264
        * init.c (__gnat_alternate_sta) [Linux]: Remove preprocessor test on
        MINSIGSTKSZ and bump size to 32KB.
        * libgnarl/s-osinte__linux.ads (Alternate_Stack_Size): Bump to 32KB.

-- 
Eric Botcazou
diff --git a/gcc/ada/init.c b/gcc/ada/init.c
index e76aa79c5a8..3ceb1a31b02 100644
--- a/gcc/ada/init.c
+++ b/gcc/ada/init.c
@@ -579,12 +579,8 @@ __gnat_error_handler (int sig, siginfo_t *si ATTRIBUTE_UNUSED, void *ucontext)
 
 #ifndef __ia64__
 #define HAVE_GNAT_ALTERNATE_STACK 1
-/* This must be in keeping with System.OS_Interface.Alternate_Stack_Size.
-   It must be larger than MINSIGSTKSZ and hopefully near 2 * SIGSTKSZ.  */
-# if 16 * 1024 < MINSIGSTKSZ
-#  error "__gnat_alternate_stack too small"
-# endif
-char __gnat_alternate_stack[16 * 1024];
+/* This must be in keeping with System.OS_Interface.Alternate_Stack_Size.  */
+char __gnat_alternate_stack[32 * 1024];
 #endif
 
 #ifdef __XENO__
diff --git a/gcc/ada/libgnarl/s-osinte__linux.ads b/gcc/ada/libgnarl/s-osinte__linux.ads
index f7af00bf5e2..2272f83d68d 100644
--- a/gcc/ada/libgnarl/s-osinte__linux.ads
+++ b/gcc/ada/libgnarl/s-osinte__linux.ads
@@ -328,7 +328,7 @@ package System.OS_Interface is
       oss : access stack_t) return int;
    pragma Import (C, sigaltstack, "sigaltstack");
 
-   Alternate_Stack_Size : constant := 16 * 1024;
+   Alternate_Stack_Size : constant := 32 * 1024;
    --  This must be in keeping with init.c:__gnat_alternate_stack
 
    Alternate_Stack : aliased char_array (1 .. Alternate_Stack_Size);