dev-lang/ocaml: fix 4.09 with glibc 2.34

Bug: https://bugs.gentoo.org/804498
See: https://github.com/gentoo/gentoo/pull/22851#pullrequestreview-882504245
Signed-off-by: Sam James <sam@gentoo.org>

1 files changed, 193 insertions, 0 deletions

diff --git a/dev-lang/ocaml/files/ocaml-4.09.0-glibc-2.34.patch b/dev-lang/ocaml/files/ocaml-4.09.0-glibc-2.34.patch
new file mode 100644
index 000000000000..6f74d38e80b6
--- /dev/null
+++ b/dev-lang/ocaml/files/ocaml-4.09.0-glibc-2.34.patch
@@ -0,0 +1,193 @@
+https://github.com/ocaml/ocaml/commit/8eed2e441222588dc385a98ae8bd6f5820eb0223
+https://github.com/gentoo/gentoo/pull/22851#pullrequestreview-882504245
+
+From 8eed2e441222588dc385a98ae8bd6f5820eb0223 Mon Sep 17 00:00:00 2001
+From: Xavier Leroy <xavierleroy@users.noreply.github.com>
+Date: Fri, 5 Mar 2021 19:14:07 +0100
+Subject: [PATCH] Dynamically allocate the alternate signal stack
+
+In Glibc 2.34 and later, SIGSTKSZ may not be a compile-time constant.
+It is no longer possible to statically allocate the alternate signal
+stack for the main thread, as we've been doing for the last 25 years.
+
+This commit implements dynamic allocation of the alternate signal stack
+even for the main thread.  It reuses the code already in place to allocate
+the alternate signal stack for other threads.
+
+The alternate signal stack is freed when the main OCaml code / an OCaml thread
+stops.
+
+(partial back-port of PR#10266 and PR#10726)
+---
+ runtime/fail_nat.c    |  7 ++++-
+ runtime/signals_nat.c | 64 +++++++++++++++++++++++++++++++++++++------
+ runtime/startup_nat.c |  7 ++++-
+ runtime/sys.c         |  5 ++++
+ 4 files changed, 72 insertions(+), 11 deletions(-)
+
+diff --git a/runtime/fail_nat.c b/runtime/fail_nat.c
+index e1f687d379e..cbf7633ee9e 100644
+--- a/runtime/fail_nat.c
++++ b/runtime/fail_nat.c
+@@ -31,6 +31,8 @@
+ #include "caml/roots.h"
+ #include "caml/callback.h"
+ 
++extern void caml_terminate_signals(void);
++
+ /* The globals holding predefined exceptions */
+ 
+ typedef value caml_generated_constant[1];
+@@ -60,7 +62,10 @@ char * caml_exception_pointer = NULL;
+ void caml_raise(value v)
+ {
+   Unlock_exn();
+-  if (caml_exception_pointer == NULL) caml_fatal_uncaught_exception(v);
++  if (caml_exception_pointer == NULL) {
++    caml_terminate_signals();
++    caml_fatal_uncaught_exception(v);
++  }
+ 
+   while (caml_local_roots != NULL &&
+          (char *) caml_local_roots < caml_exception_pointer) {
+diff --git a/runtime/signals_nat.c b/runtime/signals_nat.c
+index 29a5f49e625..351b575a08e 100644
+--- a/runtime/signals_nat.c
++++ b/runtime/signals_nat.c
+@@ -182,7 +182,6 @@ DECLARE_SIGNAL_HANDLER(trap_handler)
+ #ifdef HAS_STACK_OVERFLOW_DETECTION
+ 
+ static char * system_stack_top;
+-static char sig_alt_stack[SIGSTKSZ];
+ 
+ #if defined(SYS_linux)
+ /* PR#4746: recent Linux kernels with support for stack randomization
+@@ -275,14 +274,61 @@ void caml_init_signals(void)
+   {
+     stack_t stk;
+     struct sigaction act;
+-    stk.ss_sp = sig_alt_stack;
+-    stk.ss_size = SIGSTKSZ;
+-    stk.ss_flags = 0;
+-    SET_SIGACT(act, segv_handler);
+-    act.sa_flags |= SA_ONSTACK | SA_NODEFER;
+-    sigemptyset(&act.sa_mask);
+-    system_stack_top = (char *) &act;
+-    if (sigaltstack(&stk, NULL) == 0) { sigaction(SIGSEGV, &act, NULL); }
++    /* Allocate and select an alternate stack for handling signals,
++       especially SIGSEGV signals.
++       The alternate stack used to be statically-allocated for the main thread,
++       but this is incompatible with Glibc 2.34 and newer, where SIGSTKSZ
++       may not be a compile-time constant. */
++    stk.ss_sp = malloc(SIGSTKSZ);
++    if (stk.ss_sp != NULL) {
++      stk.ss_size = SIGSTKSZ;
++      stk.ss_flags = 0;
++      SET_SIGACT(act, segv_handler);
++      act.sa_flags |= SA_ONSTACK | SA_NODEFER;
++      sigemptyset(&act.sa_mask);
++      system_stack_top = (char *) &act;
++      if (sigaltstack(&stk, NULL) == 0)
++        sigaction(SIGSEGV, &act, NULL);
++      else
++        free(stk.ss_sp);
++    }
++  }
++#endif
++}
++
++/* Termination of signal stuff */
++
++#if defined(TARGET_power) || defined(TARGET_s390x) \
++    || defined(HAS_STACK_OVERFLOW_DETECTION)
++static void set_signal_default(int signum)
++{
++  struct sigaction act;
++  sigemptyset(&act.sa_mask);
++  act.sa_handler = SIG_DFL;
++  act.sa_flags = 0;
++  sigaction(signum, &act, NULL);
++}
++#endif
++
++void caml_terminate_signals(void)
++{
++#if defined(TARGET_power)
++  set_signal_default(SIGTRAP);
++#endif
++
++#if defined(TARGET_s390x)
++  set_signal_default(SIGFPE);
++#endif
++
++#ifdef HAS_STACK_OVERFLOW_DETECTION
++  set_signal_default(SIGSEGV);
++  stack_t oldstk, stk;
++  stk.ss_flags = SS_DISABLE;
++  if (sigaltstack(&stk, &oldstk) == 0) {
++    /* If caml_init_signals failed, we are not using an alternate signal stack.
++       SS_DISABLE will be set in oldstk, and there is nothing to free in this
++       case. */
++    if (! (oldstk.ss_flags & SS_DISABLE)) free(oldstk.ss_sp);
+   }
+ #endif
+ }
+diff --git a/runtime/startup_nat.c b/runtime/startup_nat.c
+index 7eca5fa5581..f52bec980b6 100644
+--- a/runtime/startup_nat.c
++++ b/runtime/startup_nat.c
+@@ -92,6 +92,7 @@ void (*caml_termination_hook)(void *) = NULL;
+ extern value caml_start_program (void);
+ extern void caml_init_ieee_floats (void);
+ extern void caml_init_signals (void);
++extern void caml_terminate_signals(void);
+ #ifdef _WIN32
+ extern void caml_win32_overflow_detection (void);
+ #endif
+@@ -106,6 +107,7 @@ extern void caml_install_invalid_parameter_handler();
+ value caml_startup_common(char_os **argv, int pooling)
+ {
+   char_os * exe_name, * proc_self_exe;
++  value res;
+   char tos;
+ 
+   /* Determine options */
+@@ -153,10 +155,13 @@ value caml_startup_common(char_os **argv, int pooling)
+     exe_name = caml_search_exe_in_path(exe_name);
+   caml_sys_init(exe_name, argv);
+   if (sigsetjmp(caml_termination_jmpbuf.buf, 0)) {
++    caml_terminate_signals();
+     if (caml_termination_hook != NULL) caml_termination_hook(NULL);
+     return Val_unit;
+   }
+-  return caml_start_program();
++  res = caml_start_program();
++  caml_terminate_signals();
++  return res;
+ }
+ 
+ value caml_startup_exn(char_os **argv)
+diff --git a/runtime/sys.c b/runtime/sys.c
+index 226d596cdff..9e201354e1e 100644
+--- a/runtime/sys.c
++++ b/runtime/sys.c
+@@ -112,6 +112,8 @@ static void caml_sys_check_path(value name)
+   }
+ }
+ 
++extern void caml_terminate_signals(void);
++
+ CAMLprim value caml_sys_exit(value retcode_v)
+ {
+   int retcode = Int_val(retcode_v);
+@@ -155,6 +157,9 @@ CAMLprim value caml_sys_exit(value retcode_v)
+     caml_shutdown();
+ #ifdef _WIN32
+   caml_restore_win32_terminal();
++#endif
++#ifdef NATIVE_CODE
++  caml_terminate_signals();
+ #endif
+   exit(retcode);
+ }
+