nixpkgs/pkgs/development/compilers/sbcl/dynamic-space-size-envvar-2.5.3-feature.patch

From 9c899f7b8089eee7ce471f237d2046882298c4fc Mon Sep 17 00:00:00 2001
From: Hraban Luyat <hraban@0brg.net>
Date: Sat, 13 Apr 2024 14:04:57 -0400
Subject: [PATCH 1/2] feat: NIX_SBCL_DYNAMIC_SPACE_SIZE envvar

---
 src/runtime/runtime.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
index 2b1f8b634..4f3f51139 100644
--- a/src/runtime/runtime.c
+++ b/src/runtime/runtime.c
@@ -416,6 +416,29 @@ 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)
@@ -457,6 +480,9 @@ parse_argv(struct memsize_options memsize_options,
         thread_control_stack_size = memsize_options.thread_control_stack_size;
         dynamic_values_bytes = memsize_options.thread_tls_bytes;
         if (memsize_options.present_in_core == 2) {
+            /* Only accept environment variable memory options where you would
+             * accept those options as command-line arguments. */
+            read_memsize_from_env();
             int stop_parsing = 0; // have we seen '--'
             int output_index = 1;
 #ifndef LISP_FEATURE_WIN32
@@ -490,6 +516,7 @@ parse_argv(struct memsize_options memsize_options,
 #endif
         }
     } 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 */
-- 
2.48.1