dev-lang/ocaml: fix build with glibc 2.34

Closes: https://bugs.gentoo.org/816765
Signed-off-by: Sam James <sam@gentoo.org>

3 files changed, 99 insertions, 0 deletions

diff --git a/dev-lang/ocaml/files/ocaml-4.12.0-glibc-2.34.patch b/dev-lang/ocaml/files/ocaml-4.12.0-glibc-2.34.patch
new file mode 100644
index 000000000000..486b44846a86
--- /dev/null
+++ b/dev-lang/ocaml/files/ocaml-4.12.0-glibc-2.34.patch
@@ -0,0 +1,91 @@
+https://src.fedoraproject.org/rpms/ocaml/blob/129153b85109944bf0b2922949f77ef8f32b39a1/f/0004-Dynamically-allocate-the-alternate-signal-stack-1026.patch
+https://bugs.gentoo.org/816765
+
+From 3104d92743614f8f52039e0520116af4179880a5 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 4/4] Dynamically allocate the alternate signal stack (#10266)
+
+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.
+
+Fixes: #10250.
+(cherry picked from commit fc9534746bf5d08a4c109f22e344cf49d5d46d54)
+--- a/runtime/caml/signals.h
++++ b/runtime/caml/signals.h
+@@ -87,7 +87,7 @@ value caml_do_pending_actions_exn (void);
+ value caml_process_pending_actions_with_root (value extra_root); // raises
+ value caml_process_pending_actions_with_root_exn (value extra_root);
+ int caml_set_signal_action(int signo, int action);
+-CAMLextern void caml_setup_stack_overflow_detection(void);
++CAMLextern int caml_setup_stack_overflow_detection(void);
+ 
+ CAMLextern void (*caml_enter_blocking_section_hook)(void);
+ CAMLextern void (*caml_leave_blocking_section_hook)(void);
+--- a/runtime/signals_byt.c
++++ b/runtime/signals_byt.c
+@@ -81,4 +81,4 @@ int caml_set_signal_action(int signo, int action)
+     return 0;
+ }
+ 
+-CAMLexport void caml_setup_stack_overflow_detection(void) {}
++CAMLexport int caml_setup_stack_overflow_detection(void) { return 0; }
+--- a/runtime/signals_nat.c
++++ b/runtime/signals_nat.c
+@@ -181,8 +181,6 @@ DECLARE_SIGNAL_HANDLER(trap_handler)
+ #error "CONTEXT_SP is required if HAS_STACK_OVERFLOW_DETECTION is defined"
+ #endif
+ 
+-static char sig_alt_stack[SIGSTKSZ];
+-
+ /* Code compiled with ocamlopt never accesses more than
+    EXTRA_STACK bytes below the stack pointer. */
+ #define EXTRA_STACK 256
+@@ -276,28 +274,33 @@ void caml_init_signals(void)
+ #endif
+ 
+ #ifdef HAS_STACK_OVERFLOW_DETECTION
+-  {
+-    stack_t stk;
++  if (caml_setup_stack_overflow_detection() != -1) {
+     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);
+-    if (sigaltstack(&stk, NULL) == 0) { sigaction(SIGSEGV, &act, NULL); }
++    sigaction(SIGSEGV, &act, NULL);
+   }
+ #endif
+ }
+ 
+-CAMLexport void caml_setup_stack_overflow_detection(void)
++/* Allocate and select an alternate stack for handling signals,
++   especially SIGSEGV signals.
++   Each thread needs its own alternate stack.
++   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 (issue #10250). */
++
++CAMLexport int caml_setup_stack_overflow_detection(void)
+ {
+ #ifdef HAS_STACK_OVERFLOW_DETECTION
+   stack_t stk;
+   stk.ss_sp = malloc(SIGSTKSZ);
++  if (stk.ss_sp == NULL) return -1;
+   stk.ss_size = SIGSTKSZ;
+   stk.ss_flags = 0;
+-  if (stk.ss_sp)
+-    sigaltstack(&stk, NULL);
++  return sigaltstack(&stk, NULL);
++#else
++  return 0;
+ #endif
+ }
diff --git a/dev-lang/ocaml/ocaml-4.12.0-r2.ebuild b/dev-lang/ocaml/ocaml-4.12.0-r2.ebuild
index da99522c6e38..287a7f38e79d 100644
--- a/dev-lang/ocaml/ocaml-4.12.0-r2.ebuild
+++ b/dev-lang/ocaml/ocaml-4.12.0-r2.ebuild
@@ -20,6 +20,10 @@ BDEPEND="${RDEPEND}
 PDEPEND="emacs? ( app-emacs/ocaml-mode )
 	xemacs? ( app-xemacs/ocaml )"
 
+PATCHES=(
+	"${FILESDIR}"/${PN}-4.12.0-glibc-2.34.patch
+)
+
 src_prepare() {
 	default
 
diff --git a/dev-lang/ocaml/ocaml-4.12.1.ebuild b/dev-lang/ocaml/ocaml-4.12.1.ebuild
index da99522c6e38..287a7f38e79d 100644
--- a/dev-lang/ocaml/ocaml-4.12.1.ebuild
+++ b/dev-lang/ocaml/ocaml-4.12.1.ebuild
@@ -20,6 +20,10 @@ BDEPEND="${RDEPEND}
 PDEPEND="emacs? ( app-emacs/ocaml-mode )
 	xemacs? ( app-xemacs/ocaml )"
 
+PATCHES=(
+	"${FILESDIR}"/${PN}-4.12.0-glibc-2.34.patch
+)
+
 src_prepare() {
 	default