From 0723a83fd6cebe059629c88a6e9e2c9ffb696534 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Tue, 6 Aug 2024 22:03:19 +0100
Subject: [PATCH] Avoid linker errors on Windows with long command lines

---
 NEWS.md    |  2 ++
 src/cgen.c | 33 +++++++++++++++++++++++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 59898d699..488fdfdcf 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -17,6 +17,8 @@
   coverage database file instead of a top-level unit name.
 - The `--force-init` command which was deprecated in the 1.7 release has
   been removed.
+- Elaboration of large designs on Windows no longer fail with linker
+  errors due to excessive command line length.
 
 ## Version 1.13.1 - 2024-07-25
 - Windows installer was missing some standard library files.
diff --git a/src/cgen.c b/src/cgen.c
index 5058c2d99..701b4017c 100644
--- a/src/cgen.c
+++ b/src/cgen.c
@@ -62,6 +62,7 @@ static A(char *) link_args;
 static A(char *) cleanup_files = AINIT;
 
 #define UNITS_PER_JOB 25
+#define LARGE_OBJECT_COUNT 10
 
 static void cgen_find_children(vcode_unit_t root, unit_list_t *units)
 {
@@ -215,8 +216,29 @@ static void cgen_link(const char *module_name, char **objs, int nobjs)
    cgen_link_arg("-o");
    cgen_link_arg("%s", so_path);
 
-   for (int i = 0; i < nobjs; i++)
-      cgen_link_arg("%s", objs[i]);
+   char *tmplist = NULL;
+   if (nobjs >= LARGE_OBJECT_COUNT) {
+      // If there are a large number of objects to link then pass them
+      // in a file rather than individually to avoid command line length
+      // limits on Windows
+
+      tmplist = nvc_temp_file();
+
+      FILE *f = fopen(tmplist, "w");
+      if (f == NULL)
+         fatal_errno("%s", tmplist);
+
+      for (int i = 0; i < nobjs; i++)
+         fprintf(f, "%s\n", objs[i]);
+
+      fclose(f);
+
+      cgen_link_arg("@%s", tmplist);
+   }
+   else {
+      for (int i = 0; i < nobjs; i++)
+         cgen_link_arg("%s", objs[i]);
+   }
 
 #if defined LINKER_PATH && defined __OpenBSD__
    // Extra linker arguments to make constructors work on OpenBSD
@@ -250,6 +272,13 @@ static void cgen_link(const char *module_name, char **objs, int nobjs)
          fatal_errno("unlink: %s", objs[i]);
    }
 
+   if (tmplist != NULL) {
+      if (unlink(tmplist) != 0)
+         fatal_errno("unlink: %s", tmplist);
+
+      free(tmplist);
+   }
+
    progress("linking shared library");
 
    for (size_t i = 0; i < link_args.count; i++)