From e4f79b7167312dab649218b53b84c0829ea0c103 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Mon, 10 May 2021 11:38:48 -0400
Subject: [PATCH] [CLI] ensure error on not finding symbol (#40748)

This sanity check was attempted in #38994, but dlsym is often also okay
with finding the trampoline, so we want to also check that it does not
use that to resolve the trampoline ad infinitum.
---
 cli/jl_exports.h | 14 ++++++++++----
 cli/loader_lib.c |  2 +-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/cli/jl_exports.h b/cli/jl_exports.h
index 0d467a6528b75..35d2767726865 100644
--- a/cli/jl_exports.h
+++ b/cli/jl_exports.h
@@ -10,13 +10,19 @@
 JL_EXPORTED_DATA_POINTERS(XX)
 #undef XX
 
-// Define symbol data as `$type) $(name);`
+// Define symbol data as `$(type) $(name);`
 #define XX(name, type)    JL_DLLEXPORT type name;
 JL_EXPORTED_DATA_SYMBOLS(XX)
 #undef XX
 
-// Define holder locations for function addresses as `const void * $(name)_addr`
-#define XX(name)    JL_HIDDEN const void * name##_addr;
+// Declare list of exported functions (sans type)
+#define XX(name)    JL_DLLEXPORT void name(void);
+typedef void (anonfunc)(void);
+JL_EXPORTED_FUNCS(XX)
+#undef XX
+
+// Define holder locations for function addresses as `const void * $(name)_addr = & $(name);`
+#define XX(name)    JL_HIDDEN anonfunc * name##_addr = (anonfunc*)&name;
 JL_EXPORTED_FUNCS(XX)
 #undef XX
 
@@ -29,7 +35,7 @@ static const char *const jl_exported_func_names[] = {
 #undef XX
 
 #define XX(name)    &name##_addr,
-static const void ** jl_exported_func_addrs[] = {
+static anonfunc **const jl_exported_func_addrs[] = {
     JL_EXPORTED_FUNCS(XX)
     NULL
 };
diff --git a/cli/loader_lib.c b/cli/loader_lib.c
index 2f596ac27202d..f7858d9bc909f 100644
--- a/cli/loader_lib.c
+++ b/cli/loader_lib.c
@@ -161,7 +161,7 @@ __attribute__((constructor)) void jl_load_libjulia_internal(void) {
     // Once we have libjulia-internal loaded, re-export its symbols:
     for (unsigned int symbol_idx=0; jl_exported_func_names[symbol_idx] != NULL; ++symbol_idx) {
         void *addr = lookup_symbol(libjulia_internal, jl_exported_func_names[symbol_idx]);
-        if (addr == NULL) {
+        if (addr == NULL || addr == *jl_exported_func_addrs[symbol_idx]) {
             jl_loader_print_stderr3("ERROR: Unable to load ", jl_exported_func_names[symbol_idx], " from libjulia-internal");
             exit(1);
         }