Test for libunwind in ./configure

blink/debug.c

@@ -49,7 +49,7 @@
 #include <sched.h>
 #endif
 
-#ifdef UNWIND
+#if defined(HAVE_LIBUNWIND) && !defined(MUSL_CROSS_MAKE)
 #define UNW_LOCAL_ONLY
 #include <libunwind.h>
 #endif
@@ -63,7 +63,7 @@
 _Thread_local static jmp_buf g_busted;
 
 const char *GetBlinkBacktrace(void) {
-#ifdef UNWIND
+#if defined(HAVE_LIBUNWIND) && !defined(MUSL_CROSS_MAKE)
   _Thread_local static char b[2048];
   int o = 0;
   char sym[256];

build/config.mk

@@ -25,6 +25,9 @@ ifeq ($(HOST_SYSTEM), FreeBSD)
 LDFLAGS += -Wl,--image-base=$(IMAGE_BASE_VIRTUAL)
 endif
 
+# Tune the build when using our prebuilt musl-cross-make toolchains.
+CPPFLAGS_STATIC =			\
+	-DMUSL_CROSS_MAKE
 LDFLAGS_STATIC =			\
 	-static				\
 	-fno-exceptions			\
@@ -60,12 +63,6 @@ endif
 ifeq ($(MODE), dbg)
 CFLAGS += -O0 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer
 CPPFLAGS += -DDEBUG
-ifneq ($(HOST_SYSTEM), Darwin)
-ifneq ($(HOST_SYSTEM), FreeBSD)
-CPPFLAGS += -DUNWIND
-LDLIBS += -lunwind -llzma
-endif
-endif
 endif
 
 ifeq ($(MODE), rel)

config.h.in

@@ -39,6 +39,7 @@
 // #define HAVE_KERN_ARND
 // #define HAVE_GETRANDOM
 // #define HAVE_SETGROUPS
+// #define HAVE_LIBUNWIND
 // #define HAVE_GETENTROPY
 // #define HAVE_MAP_SHARED
 // #define HAVE_SENDTO_ZERO

configure

@@ -230,8 +230,8 @@ compile() {
       ${TARGET_ARCH} \
       "$@" \
       ${LOADLIBES} \
-      ${LDLIBS} \
-      ${EXTRA_LDLIBS}
+      ${EXTRA_LDLIBS} \
+      ${LDLIBS}
 }
 
 config() {
@@ -476,13 +476,7 @@ fi
 # check for the math library
 EXTRA_LDLIBS=-lm
 if config lm "checking for -lm... "; then
-  LDLIBS="${LDLIBS} -lm"
-fi
-
-# check for the posix.1b realtime extensions library
-EXTRA_LDLIBS=-lrt
-if config lrt "checking for -lrt... "; then
-  LDLIBS="${LDLIBS} -lrt"
+  LDLIBS="-lm ${LDLIBS}"
 fi
 
 # check for the posix threads library
@@ -495,17 +489,24 @@ if [ -z "${DISABLE_THREADS}" ]; then
   else
     EXTRA_LDLIBS=-lpthread
     if config pthread "checking for -lpthread... "; then
-      LDLIBS="${LDLIBS} -lpthread"
+      LDLIBS="-lpthread ${LDLIBS}"
     else
       if config pthread "checking for pthreads... "; then
-        LDLIBS="${LDLIBS} -lpthread"
+        LDLIBS="-lpthread ${LDLIBS}"
       else
         uncomment "#define DISABLE_THREADS"
       fi
     fi
   fi
 fi
 
+# check for the posix.1b realtime extensions library
+# note: librt depends on pthreads, on rhel5 at least
+EXTRA_LDLIBS=-lrt
+if config lrt "checking for -lrt... "; then
+  LDLIBS="-lrt ${LDLIBS}"
+fi
+
 # should be the default and macos build fails without it
 EXTRA_CFLAGS=-fno-common
 if config noop "checking for -fno-common... "; then
@@ -566,6 +567,21 @@ if [ -z "${MODE}" ] && [ -n "${JIT_POSSIBLE}" ] && [ -z "${DISABLE_JIT}" ]; then
   fi
 fi
 
+# try to get blink backtraces if possible
+if [ "${MODE}" != "tiny" ] && [ "${MODE}" != "rel" ]; then
+  UNWIND_CFLAGS="$(pkg-config --cflags libunwind 2>/dev/null)"
+  if ! UNWIND_LDLIBS="$(pkg-config --libs libunwind 2>/dev/null)"; then
+    UNWIND_LDLIBS="-lunwind -llzma"
+  fi
+  EXTRA_CFLAGS="${UNWIND_CFLAGS}"
+  EXTRA_LDLIBS="${UNWIND_LDLIBS}"
+  if config lrt "checking for libunwind... "; then
+    CFLAGS="${UNWIND_CFLAGS} ${CFLAGS}"
+    LDLIBS="${UNWIND_LDLIBS} ${LDLIBS}"
+    uncomment "#define HAVE_LIBUNWIND"
+  fi
+fi
+
 # attempt to polyfill c11 atomics if it's not available
 if ! config stdatomic "checking for stdatomic.h... "; then
   CPPFLAGS="-isystem tool/stdatomic"

tool/config/config.mk

@@ -2,4 +2,7 @@
 #───vi: set et ft=make ts=8 tw=8 fenc=utf-8 :vi───────────────────────┘
 
 o/$(MODE)/tool/config/%.com: tool/config/%.c
-	$(CC) -o $@ $<
+	@mkdir -p $(@D)
+	$(CC) -o $@ $< $(LDLIBS)
+
+o/$(MODE)/tool/config/libunwind.com: private LDLIBS += -lunwind -lucontext -llzma

tool/config/libunwind.c

@@ -0,0 +1,45 @@
+// checks for libunwind backtrace support
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
+#include <stdio.h>
+#include <string.h>
+
+#define APPEND(...) o += snprintf(b + o, n - o, __VA_ARGS__)
+
+const char *GetBacktrace(void) {
+  static char b[2048];
+  int o = 0;
+  char sym[256];
+  int n = sizeof(b);
+  unw_cursor_t cursor;
+  unw_context_t context;
+  unw_word_t offset, pc;
+  unw_getcontext(&context);
+  unw_init_local(&cursor, &context);
+  APPEND("backtrace");
+  while (unw_step(&cursor) > 0) {
+    unw_get_reg(&cursor, UNW_REG_IP, &pc);
+    if (!pc) break;
+    APPEND("\n\t%lx ", pc);
+    if (unw_get_proc_name(&cursor, sym, sizeof(sym), &offset) == 0) {
+      APPEND("%s+%ld", sym, offset);
+    } else {
+      APPEND("<unknown>");
+    }
+  }
+  return b;
+}
+
+const char *MyApp(void) {
+  return GetBacktrace();
+}
+
+const char *(*MyAppPtr)(void) = MyApp;
+
+int main(int argc, char *argv[]) {
+  const char *bt;
+  bt = MyAppPtr();
+  if (!strstr(bt, "MyApp")) return 1;
+  if (!strstr(bt, "main")) return 2;
+  return 0;
+}