From fa126b950ae3d19876276466e8b3f9e48230a722 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Wed, 25 Nov 2020 15:40:17 +0200
Subject: [PATCH] cgen: prevent `undefined symbol: tcc_backtrace` errors with
 tcc and `-shared -d no_backtrace`

---
 vlib/builtin/builtin_nix.c.v |  8 ++++----
 vlib/v/builder/cc.v          |  2 +-
 vlib/v/gen/cheaders.v        | 18 ++++++++++++++++++
 vlib/v/gen/fn.v              |  6 +++---
 4 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/vlib/builtin/builtin_nix.c.v b/vlib/builtin/builtin_nix.c.v
index 9a75f4bf18..b305465b8a 100644
--- a/vlib/builtin/builtin_nix.c.v
+++ b/vlib/builtin/builtin_nix.c.v
@@ -83,13 +83,13 @@ fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
 		eprintln('Some libc implementations like musl simply do not provide it.')
 		return false
 	}
-	$if tinyc {
-		C.tcc_backtrace("Backtrace")
-		return false
-	}
 	$if no_backtrace ? {
 		return false
 	} $else {
+		$if tinyc {
+			C.tcc_backtrace("Backtrace")
+			return false
+		}
 		buffer := [100]byteptr{}
 		nr_ptrs := C.backtrace(voidptr(buffer), 100)
 		if nr_ptrs < 2 {
diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index 7cc2c6efe4..da2af815d9 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -497,7 +497,7 @@ fn (mut v Builder) cc() {
 			}
 		}
 	}
-	if is_cc_tcc {
+	if is_cc_tcc && 'no_backtrace' !in v.pref.compile_defines {
 		args << '-bt25'
 	}
 	// Without these libs compilation will fail on Linux
diff --git a/vlib/v/gen/cheaders.v b/vlib/v/gen/cheaders.v
index c572d75229..1fc60628ca 100644
--- a/vlib/v/gen/cheaders.v
+++ b/vlib/v/gen/cheaders.v
@@ -99,6 +99,24 @@ typedef int (*qsort_callback_func)(const void*, const void*);
 #include <stdio.h>  // TODO remove all these includes, define all function signatures and types manually
 #include <stdlib.h>
 
+#if defined(_WIN32) || defined(__CYGWIN__)
+	#define VV_EXPORTED_SYMBOL extern __declspec(dllexport)
+	#define VV_LOCAL_SYMBOL static
+#else
+	// 4 < gcc < 5 is used by some older Ubuntu LTS and Centos versions,
+	// and does not support __has_attribute(visibility) ...
+	#ifndef __has_attribute
+		#define __has_attribute(x) 0  // Compatibility with non-clang compilers.
+	#endif
+	#if (defined(__GNUC__) && (__GNUC__ >= 4)) || (defined(__clang__) && __has_attribute(visibility))
+		#define VV_EXPORTED_SYMBOL extern __attribute__ ((visibility ("default")))
+		#define VV_LOCAL_SYMBOL  __attribute__ ((visibility ("hidden")))
+	#else
+		#define VV_EXPORTED_SYMBOL extern
+		#define VV_LOCAL_SYMBOL static
+	#endif
+#endif
+
 #ifdef __cplusplus
 	#include <utility>
 	#define _MOV std::move
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index 4d7486fce3..da56b0e8c1 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -100,8 +100,8 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 				// if !(g.pref.build_mode == .build_module && g.is_builtin_mod) {
 				// If we are building vlib/builtin, we need all private functions like array_get
 				// to be public, so that all V programs can access them.
-				g.write('static ')
-				g.definitions.write('static ')
+				g.write('VV_LOCAL_SYMBOL ')
+				g.definitions.write('VV_LOCAL_SYMBOL ')
 			}
 		}
 		fn_header := if msvc_attrs.len > 0 { '$type_name $msvc_attrs ${name}(' } else { '$type_name ${name}(' }
@@ -170,7 +170,7 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 		if attr.name == 'export' {
 			g.writeln('// export alias: $attr.arg -> $name')
 			export_alias := '$type_name ${attr.arg}($arg_str)'
-			g.definitions.writeln('$export_alias;')
+			g.definitions.writeln('VV_EXPORTED_SYMBOL $export_alias; // exported fn $it.name')
 			g.writeln('$export_alias {')
 			g.write('\treturn ${name}(')
 			g.write(fargs.join(', '))