From c92654a044166a07b72cb4d314bbe68220b28855 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Wed, 28 Aug 2019 19:26:18 +0300
Subject: [PATCH] fix building v on alpine with musl libc

---
 compiler/cheaders.v    |  2 ++
 vlib/builtin/builtin.v | 15 ++++++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/compiler/cheaders.v b/compiler/cheaders.v
index 0d1a542d7c..e6650785ca 100644
--- a/compiler/cheaders.v
+++ b/compiler/cheaders.v
@@ -23,6 +23,8 @@ CommonCHeaders = '
 
 #ifdef __linux__
 #include <execinfo.h> // backtrace and backtrace_symbols_fd
+#pragma weak backtrace
+#pragma weak backtrace_symbols_fd
 #endif
 
 #ifdef __linux__
diff --git a/vlib/builtin/builtin.v b/vlib/builtin/builtin.v
index aa6dd4b2b5..7c02cf973c 100644
--- a/vlib/builtin/builtin.v
+++ b/vlib/builtin/builtin.v
@@ -19,16 +19,21 @@ fn on_panic(f fn (int) int) {
 
 pub fn print_backtrace_skipping_top_frames(skipframes int) {
 	$if mac {
-		buffer := [100]voidptr
+		buffer := [100]byteptr
 		nr_ptrs := C.backtrace(buffer, 100)
 		C.backtrace_symbols_fd(&buffer[skipframes], nr_ptrs-skipframes, 1)
 		return
 	}
 	$if linux {
-		buffer := [100]voidptr
-		nr_ptrs := C.backtrace(buffer, 100)
-		C.backtrace_symbols_fd(&buffer[skipframes], nr_ptrs-skipframes, 1)
-		return
+		if C.backtrace_symbols_fd != 0 {
+			buffer := [100]byteptr
+			nr_ptrs := C.backtrace(buffer, 100)
+			C.backtrace_symbols_fd(&buffer[skipframes], nr_ptrs-skipframes, 1)
+			return
+		}else{
+			C.printf('backtrace_symbols_fd is missing, so printing backtraces is not available.\n')
+			C.printf('Some libc implementations like musl simply do not provide it.\n')
+		}
 	}
 	C.printf('print_backtrace_skipping_top_frames is not implemented on this platform for now...\n')
 }