sbcl: custom patch to read memory from envvar

pkgs/development/compilers/sbcl/default.nix

@@ -113,6 +113,14 @@ stdenv.mkDerivation (self: rec {
     # have it block a release.
     "futex-wait.test.sh"
   ];
+  patches = [
+    # Support the NIX_SBCL_DYNAMIC_SPACE_SIZE envvar. Upstream SBCL didn’t want
+    # to include this (see
+    # "https://sourceforge.net/p/sbcl/mailman/sbcl-devel/thread/2cf20df7-01d0-44f2-8551-0df01fe55f1a%400brg.net/"),
+    # but for Nix envvars are sufficiently useful that it’s worth maintaining
+    # this functionality downstream.
+    ./dynamic-space-size-envvar-feature.patch
+  ];
   postPatch = lib.optionalString (self.disabledTestFiles != [ ]) ''
     (cd tests ; rm -f ${lib.concatStringsSep " " self.disabledTestFiles})
   ''

pkgs/development/compilers/sbcl/dynamic-space-size-envvar-feature.patch

@@ -0,0 +1,63 @@
+From ac15f9f7c75c1fb5767514e64b609e2a75e6fe9d Mon Sep 17 00:00:00 2001
+From: Hraban Luyat <hraban@0brg.net>
+Date: Sat, 13 Apr 2024 14:04:57 -0400
+Subject: [PATCH] feat: NIX_SBCL_DYNAMIC_SPACE_SIZE envvar
+
+Read SBCL dynamic space size configuration from env if available.
+---
+ src/runtime/runtime.c | 25 +++++++++++++++++++++++++
+ 1 file changed, 25 insertions(+)
+
+diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
+index 274687c8f..970caa8f4 100644
+--- a/src/runtime/runtime.c
++++ b/src/runtime/runtime.c
+@@ -422,6 +422,29 @@ static int is_memsize_arg(char *argv[], int argi, int argc, int *merge_core_page
+     return 0;
+ }
+ 
++/**
++ * Read memory options from the environment, if present.
++ *
++ * Memory settings are read in the following priority:
++ *
++ * 1. command line arguments
++ * 2. environment variable
++ * 3. embedded options in core
++ * 4. default
++ */
++static void
++read_memsize_from_env(void) {
++  const char *val = getenv("NIX_SBCL_DYNAMIC_SPACE_SIZE");
++  // The distinction is blurry between setting an envvar to the empty string and
++  // unsetting it entirely. Depending on the calling environment it can even be
++  // tricky to properly unset an envvar in the first place. An empty envvar is
++  // practically always intended to just mean “unset”, so let’s interpret it
++  // that way.
++  if (val != NULL && (strcmp(val, "") != 0)) {
++    dynamic_space_size = parse_size_arg(val, "NIX_SBCL_DYNAMIC_SPACE_SIZE");
++  }
++}
++
+ static struct cmdline_options
+ parse_argv(struct memsize_options memsize_options,
+            int argc, char *argv[], char *envp[], char *core)
+@@ -462,6 +485,7 @@ parse_argv(struct memsize_options memsize_options,
+         dynamic_space_size = memsize_options.dynamic_space_size;
+         thread_control_stack_size = memsize_options.thread_control_stack_size;
+         dynamic_values_bytes = memsize_options.thread_tls_bytes;
++        read_memsize_from_env();
+         int stop_parsing = 0; // have we seen '--'
+         int output_index = 1;
+ 
+@@ -488,6 +512,7 @@ parse_argv(struct memsize_options memsize_options,
+         }
+         sbcl_argv[output_index] = 0;
+     } else {
++        read_memsize_from_env();
+         bool end_runtime_options = 0;
+         /* Parse our any of the command-line options that we handle from C,
+          * stopping at the first one that we don't, and leave the rest */
+-- 
+2.44.0
+