build: remove optional support for libunwind

backtrace() was only ever used for bringup, not actually meant to be used
in any production capacity.

config.h.meson

@@ -14,8 +14,6 @@
 
 #mesondefine GETTEXT_PACKAGE
 
-#mesondefine HAVE_EXECINFO_H
-
 #mesondefine HAVE_LIBSYSTEMD
 
 #mesondefine HAVE_PERF_CLOCKID

meson.build

@@ -92,7 +92,6 @@ if get_option('default_library') != 'static'
   endif
 endif
 
-config_h.set('HAVE_EXECINFO_H', cc.has_header('execinfo.h'))
 config_h.set('HAVE_REALLOCARRAY', cc.has_function('reallocarray'))
 config_h.set('HAVE_STRLCPY', cc.has_function('strlcpy'))
 config_h.set('LOCALEDIR', 'PACKAGE_LOCALE_DIR')
@@ -107,16 +106,13 @@ config_h.set10('HAVE_POLKIT_AGENT', polkit_agent_dep.found())
 polkit_dep = dependency('polkit-gobject-1', version: polkit_req_version, required: false)
 config_h.set10('HAVE_POLKIT', polkit_dep.found())
 
-if get_option('libunwind')
-  # Force libunwind usage if it's specified to avoid back compiles
-  # and backtrace() showing up in builds
+if get_option('libsysprof')
   libunwind_dep = dependency('libunwind-generic', required: true)
   config_h.set('ENABLE_LIBUNWIND', libunwind_dep.found())
   config_h.set('HAVE_UNW_SET_CACHE_SIZE',
-               (libunwind_dep.found() and
-                 cc.has_header_symbol('libunwind.h',
-                                      'unw_set_cache_size',
-                                      dependencies: [libunwind_dep])))
+               cc.has_header_symbol('libunwind.h',
+                                    'unw_set_cache_size',
+                                    dependencies: [libunwind_dep]))
 endif
 
 # Development build setup

meson_options.txt

@@ -29,9 +29,6 @@ option('systemdunitdir', type: 'string',
 # If Yelp documentation should be installed
 option('help', type: 'boolean')
 
-# Disable use of libunwind
-option('libunwind', type: 'boolean')
-
 # Build libsysprof (required by tools, tests, sysprof, etc)
 option('libsysprof', type: 'boolean')
 

src/preload/backtrace-helper.h

@@ -20,23 +20,16 @@
 
 #pragma once
 
-#ifdef HAVE_EXECINFO_H
-# include <execinfo.h>
-#endif
-#ifdef ENABLE_LIBUNWIND
-# define UNW_LOCAL_ONLY
-# include <libunwind.h>
-#endif
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
 
 static void
 backtrace_init (void)
 {
-#ifdef ENABLE_LIBUNWIND
   unw_set_caching_policy (unw_local_addr_space, UNW_CACHE_PER_THREAD);
-# ifdef HAVE_UNW_SET_CACHE_SIZE
+#ifdef HAVE_UNW_SET_CACHE_SIZE
   unw_set_cache_size (unw_local_addr_space, 1024, 0);
 #endif
-#endif
 }
 
 static int
@@ -44,36 +37,20 @@ backtrace_func (SysprofCaptureAddress  *addrs,
                 guint                   n_addrs,
                 G_GNUC_UNUSED gpointer  user_data)
 {
-#if defined(ENABLE_LIBUNWIND)
-# if GLIB_SIZEOF_VOID_P == 8
+#if GLIB_SIZEOF_VOID_P == 8
   /* We know that collector will overwrite fields *AFTER* it
    * has called the backtrace function allowing us to cheat
    * and subtract an offset from addrs to avoid having to
    * copy frame pointers around.
    */
   return unw_backtrace ((void **)addrs - 2, n_addrs) - 2;
-# else
+#else
   static const int skip = 2;
   void **stack = alloca (n_addrs * sizeof (gpointer));
   int n = unw_backtrace (stack, n_addrs);
   for (guint i = skip; i < n; i++)
     addrs[i-skip] = GPOINTER_TO_SIZE (stack[i]);
   return MAX (0, n - skip);
-# endif
-#elif defined(HAVE_EXECINFO_H)
-# if GLIB_SIZEOF_VOID_P == 8
-  /* See note on unw_backtrace() */
-  return backtrace ((void **)addrs - 2, n_addrs) - 2;
-# else /* GLIB_SIZEOF_VOID_P != 8 */
-  static const int skip = 2;
-  void **stack = alloca (n_addrs * sizeof (gpointer));
-  int n = backtrace (stack, n_addrs);
-  for (guint i = skip; i < n; i++)
-    addrs[i-skip] = GPOINTER_TO_SIZE (stack[i]);
-  return MAX (0, n - skip);
-# endif /* GLIB_SIZEOF_VOID_P */
-#else
-  return 0;
 #endif
 }
 

src/preload/meson.build

@@ -3,14 +3,10 @@ libdl_dep = dependency('dl', required: false)
 preload_deps = [
   dependency('glib-2.0'),
   libsysprof_capture_dep,
+  libunwind_dep,
   libdl_dep,
 ]
 
-if get_option('libunwind')
-  preload_deps += [libunwind_dep]
-endif
-
-
 libsysprof_memory_preload = shared_library('sysprof-memory-@0@'.format(libsysprof_api_version),
   ['sysprof-memory-collector.c'],
   dependencies: preload_deps,