From 51f15d997162927a432db09dad13ca16b014a3e2 Mon Sep 17 00:00:00 2001
From: Michael Matz <matz@suse.de>
Date: Mon, 18 May 2020 05:15:08 +0200
Subject: [PATCH] macos: Deal with leading underscore on Mach-O

all C/C++/ObjC symbols in symbols tables have a leading underscore
in Mach-O.  Within TCC there's some confusion with tcc_add_symbol
(not adding it) and tcc_get_elf_symbol (not expecting it), and
resolve_syms (using dlsym, which doesn't expect it) and -run support.
But this sort of works.
---
 libtcc.c   | 2 +-
 tccelf.c   | 6 ++++++
 tccmacho.c | 2 +-
 tccrun.c   | 2 +-
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/libtcc.c b/libtcc.c
index 7224c521..61168deb 100644
--- a/libtcc.c
+++ b/libtcc.c
@@ -777,7 +777,7 @@ LIBTCCAPI TCCState *tcc_new(void)
     s->seg_size = 32;
 #endif
     /* enable this if you want symbols with leading underscore on windows: */
-#if 0 /* def TCC_TARGET_PE */
+#if defined TCC_TARGET_MACHO /* || defined TCC_TARGET_PE */
     s->leading_underscore = 1;
 #endif
     s->ppfp = stdout;
diff --git a/tccelf.c b/tccelf.c
index 58f24a24..99effb6b 100644
--- a/tccelf.c
+++ b/tccelf.c
@@ -932,7 +932,13 @@ ST_FUNC void relocate_syms(TCCState *s1, Section *symtab, int do_resolve)
             /* Use ld.so to resolve symbol for us (for tcc -run) */
             if (do_resolve) {
 #if defined TCC_IS_NATIVE && !defined TCC_TARGET_PE
+#ifdef TCC_TARGET_MACHO
+                /* The symbols in the symtables have a prepended '_'
+                   but dlsym() needs the undecorated name.  */
+                void *addr = dlsym(RTLD_DEFAULT, name + 1);
+#else
                 void *addr = dlsym(RTLD_DEFAULT, name);
+#endif
                 if (addr) {
                     sym->st_value = (addr_t) addr;
 #ifdef DEBUG_RELOC
diff --git a/tccmacho.c b/tccmacho.c
index 77e5454e..69af3ecc 100644
--- a/tccmacho.c
+++ b/tccmacho.c
@@ -810,7 +810,7 @@ ST_FUNC int macho_output_file(TCCState *s1, const char *filename)
         Section *s;
         collect_sections(s1, &mo);
         relocate_syms(s1, s1->symtab, 0);
-        mo.ep.entryoff = get_elf_sym_addr(s1, "main", 1) - mo.seg[1]->vmaddr;
+        mo.ep.entryoff = get_elf_sym_addr(s1, "_main", 1) - mo.seg[1]->vmaddr;
         if (s1->nb_errors)
           goto do_ret;
 
diff --git a/tccrun.c b/tccrun.c
index 8b7c9e44..92b0e647 100644
--- a/tccrun.c
+++ b/tccrun.c
@@ -140,7 +140,7 @@ LIBTCCAPI int tcc_run(TCCState *s1, int argc, char **argv)
     rt_context *rc = &g_rtctxt;
 #endif
 
-    s1->runtime_main = s1->nostdlib ? "_start" : "main";
+    s1->runtime_main = s1->nostdlib ? "_start" : s1->leading_underscore ? "_main" : "main";
     if ((s1->dflag & 16) && !find_elf_sym(s1->symtab, s1->runtime_main))
         return 0;
 #ifdef CONFIG_TCC_BACKTRACE