From 0d6a68f79e6dca830443900fee0bf51dae35bf20 Mon Sep 17 00:00:00 2001
From: Matthew Ballance <matt.ballance@gmail.com>
Date: Sun, 7 Jun 2026 14:33:55 +0000
Subject: [PATCH] Enable macOS support for dynamic load

Signed-off-by: Matthew Ballance <matt.ballance@gmail.com>
---
 src/V3EmitMk.cpp                        |  9 ++++++++-
 test_regress/t/t_flag_main_vpi.py       | 18 ++++++++++++------
 test_regress/t/t_flag_main_vpi_noexe.py |  7 ++++---
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/V3EmitMk.cpp b/src/V3EmitMk.cpp
index 2b1eca99b..c6d6c629d 100644
--- a/src/V3EmitMk.cpp
+++ b/src/V3EmitMk.cpp
@@ -738,12 +738,19 @@ public:
 
             if (v3Global.opt.vpi()) {
                 // Runtime VPI library loading (+verilator+vpi+<lib>) needs platform-specific
-                // link flags.  Resolve them with $(UNAME_S)
+                // link flags so the dlopen'd library can resolve the executable's VPI symbols.
+                // Resolve them with $(UNAME_S).
                 of.puts("# Runtime VPI library loading (+verilator+vpi+) link requirements\n");
+                // -rdynamic exports the executable's VPI symbols to the dlopen'd library;
+                // -ldl provides dlopen/dlsym.
                 of.puts("ifeq ($(UNAME_S),Linux)\n");
                 of.puts(/**/ "LDFLAGS += -rdynamic\n");
                 of.puts(/**/ "LDLIBS += -ldl\n");
                 of.puts("endif\n");
+                // macOS analog of -rdynamic; dlopen/dlsym live in libSystem so no -ldl needed.
+                of.puts("ifeq ($(UNAME_S),Darwin)\n");
+                of.puts(/**/ "LDFLAGS += -Wl,-export_dynamic\n");
+                of.puts("endif\n");
                 of.puts("\n");
             }
         }
diff --git a/test_regress/t/t_flag_main_vpi.py b/test_regress/t/t_flag_main_vpi.py
index dbb186f02..2ccadc844 100755
--- a/test_regress/t/t_flag_main_vpi.py
+++ b/test_regress/t/t_flag_main_vpi.py
@@ -7,6 +7,7 @@
 # SPDX-FileCopyrightText: 2025 Wilson Snyder
 # SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
+import platform
 import vltest_bootstrap
 
 test.scenarios('vlt')
@@ -15,13 +16,18 @@ test.scenarios('vlt')
 # Also compile a VPI shared library to be loaded at runtime via +verilator+vpi+.
 test.compile(make_pli=True, verilator_flags2=["--binary --vpi --public-flat-rw"])
 
-# With --vpi and an executable (--binary implies --exe), the Makefile must, on Linux,
-# export the executable's symbols (-rdynamic) and link libdl for the generated loader's
-# dlopen/dlsym calls.  These are gated on $(UNAME_S) so macOS/Windows are unaffected.
+# With --vpi and an executable (--binary implies --exe), the Makefile must export the
+# executable's symbols so the generated loader's dlopen'd library can resolve them.
+# The flags are gated on $(UNAME_S): -rdynamic/-ldl on Linux, -Wl,-export_dynamic on
+# macOS (Windows is unaffected, runtime loading is unsupported there).
 mk = test.obj_dir + "/V" + test.name + ".mk"
-test.file_grep(mk, r'ifeq \(\$\(UNAME_S\),Linux\)')
-test.file_grep(mk, r'LDFLAGS \+= -rdynamic')
-test.file_grep(mk, r'LDLIBS \+= -ldl')
+if platform.system() == 'Darwin':
+    test.file_grep(mk, r'ifeq \(\$\(UNAME_S\),Darwin\)')
+    test.file_grep(mk, r'LDFLAGS \+= -Wl,-export_dynamic')
+else:
+    test.file_grep(mk, r'ifeq \(\$\(UNAME_S\),Linux\)')
+    test.file_grep(mk, r'LDFLAGS \+= -rdynamic')
+    test.file_grep(mk, r'LDLIBS \+= -ldl')
 
 # Run the generated binary; load the VPI library via the +verilator+vpi+ plusarg.
 # The VPI library's output (observed 'count' reaching MAX_TICKS, then end-of-sim) is
diff --git a/test_regress/t/t_flag_main_vpi_noexe.py b/test_regress/t/t_flag_main_vpi_noexe.py
index 8daa43531..c8177a0eb 100755
--- a/test_regress/t/t_flag_main_vpi_noexe.py
+++ b/test_regress/t/t_flag_main_vpi_noexe.py
@@ -21,9 +21,10 @@ test.compile(make_main=False, verilator_make_gmake=False, verilator_flags2=["--v
 
 test.file_grep(test.obj_dir + "/V" + test.name + "_classes.mk", r'VM_VPI = 1')
 # Without --exe there is no executable to export symbols from or to dlopen into,
-# so the runtime-VPI link flags must not be emitted into the Makefile at all.
+# so the runtime-VPI link flags must not be emitted into the Makefile on any platform.
 mk = test.obj_dir + "/V" + test.name + ".mk"
-test.file_grep_not(mk, r'-rdynamic')
-test.file_grep_not(mk, r'-ldl')
+test.file_grep_not(mk, r'-rdynamic')  # Linux
+test.file_grep_not(mk, r'-ldl')  # Linux
+test.file_grep_not(mk, r'-export_dynamic')  # macOS
 
 test.passes()