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From 9bef473d17ec01efe760462271791dfaaea280c0 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date: Wed, 29 Jul 2015 22:35:19 +0200
Subject: [PATCH 1/3] configure: refactor backtrace() detection
The current code assumes that if __GLIBC__ is not defined, backtrace
support is not available, and defines BTRFS_DISABLE_BACKTRACE.
However, this macro is already defined by the configure.ac script when
--disable-backtrace is passed. This means that if you are using a C
library like musl which does not define __GLIBC__, and you pass
--disable-backtrace, you get a macro redefinition.
Instead of relying on __GLIBC__, this commit implements a proper
configure.ac based detection of backtrace support:
* If the user passes --enable-backtrace, we check if the backtrace()
function is available. If not, we abort the configure process with
an error. Otherwise we enable backtrace support by defining
HAVE_BACKTRACE.
* If the user passes --disable-backtrace, then we don't enable
backtrace support.
* If the user passes nothing special, we auto-detect: if backtrace()
is available, we use it, otherwise we simply warn at configure time
but not fail.
Upstream-status: pending
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Brendan Heading <brendanheading@gmail.com>
---
configure.ac | 32 ++++++++++++++++++++++----------
kerncompat.h | 9 ++++-----
2 files changed, 26 insertions(+), 15 deletions(-)
diff --git a/configure.ac b/configure.ac
index c3a22d1..e936a10 100644
--- a/configure.ac
+++ b/configure.ac
@@ -63,22 +63,34 @@ AC_DEFUN([PKG_STATIC], [
fi
])
-
+# Provide a --{enable,disable}-backtrace option. If not passed, set
+# enable_backtrace to 'auto' so that we try to enable backtrace
+# support if available, but if not available, we gracefully fallback
+# without backtrace support.
AC_ARG_ENABLE([backtrace],
AS_HELP_STRING([--disable-backtrace], [disable btrfs backtrace]),
- [], [enable_backtrace=yes]
+ [enable_backtrace=${enableval}], [enable_backtrace=auto]
)
-AS_IF([test "x$enable_backtrace" = xno], [
- AC_DEFINE([BTRFS_DISABLE_BACKTRACE], [1], [disable backtrace stuff in kerncompat.h ])
-])
-
-if test "x$enable_backtrace" = xyes; then
- AC_CHECK_HEADERS([execinfo.h])
- AC_CHECK_FUNCS([backtrace backtrace_symbols_fd], [],
- AC_MSG_ERROR([standard library does not have backtrace support]))
+# Backtrace support requested (enable_backtrace is either 'yes' or
+# 'auto'), so check for needed headers and functions.
+if test "x$enable_backtrace" != xno; then
+ AC_CHECK_HEADERS([execinfo.h])
+ AC_CHECK_FUNCS([backtrace backtrace_symbols_fd])
fi
+if test "x$ac_cv_func_backtrace" = xno; then
+ # If backtrace support was requested but not available, we fail if
+ # --enable-backtrace was passed, or we simply warn if we're
+ # auto-detecting.
+ if test "x$enable_backtrace" = xyes ; then
+ AC_MSG_ERROR([standard library does not have backtrace support])
+ elif test "x$enable_backtrace" = xauto ; then
+ AC_MSG_WARN([standard library does not have backtrace support, disabled])
+ fi
+else
+ AC_DEFINE([HAVE_BACKTRACE], [1], [Enable backtrace support])
+fi
AC_ARG_ENABLE([documentation],
AS_HELP_STRING([--disable-documentation], [do not build domumentation]),
diff --git a/kerncompat.h b/kerncompat.h
index 5d92856..8318665 100644
--- a/kerncompat.h
+++ b/kerncompat.h
@@ -33,11 +33,10 @@
#include <features.h>
#ifndef __GLIBC__
-#define BTRFS_DISABLE_BACKTRACE
#define __always_inline __inline __attribute__ ((__always_inline__))
#endif
-#ifndef BTRFS_DISABLE_BACKTRACE
+#ifdef HAVE_BACKTRACE
#include <execinfo.h>
#endif
@@ -65,7 +64,7 @@
#define ULONG_MAX (~0UL)
#endif
-#ifndef BTRFS_DISABLE_BACKTRACE
+#ifdef HAVE_BACKTRACE
#define MAX_BACKTRACE 16
static inline void print_trace(void)
{
@@ -285,7 +284,7 @@ static inline long IS_ERR(const void *ptr)
#define vmalloc(x) malloc(x)
#define vfree(x) free(x)
-#ifndef BTRFS_DISABLE_BACKTRACE
+#ifdef HAVE_BACKTRACE
#define BUG_ON(c) assert_trace(#c, __FILE__, __func__, __LINE__, !(c))
#else
#define BUG_ON(c) assert(!(c))
@@ -293,7 +292,7 @@ static inline long IS_ERR(const void *ptr)
#define WARN_ON(c) BUG_ON(c)
-#ifndef BTRFS_DISABLE_BACKTRACE
+#ifdef HAVE_BACKTRACE
#define ASSERT(c) assert_trace(#c, __FILE__, __func__, __LINE__, (c))
#else
#define ASSERT(c) assert(c)
--
2.4.3
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