gstinfo: Rework stack trace detection a bit

Ensure that the code paths for HAVE_UNWIND and HAVE_DBGHELP are never
taken at the same time, even if the build file code changes.

Prefer DbgHelp over libunwind on Windows in case both are somehow
available because DbgHelp is only available when building with the
MSVC toolchain, and libunwind won't give us debug symbols from objects
built with the MSVC toolchain.

Also, print slightly more useful messages for the level of stack trace
support enabled, and document what each if conditional does.

diff --git a/gst/gstinfo.c b/gst/gstinfo.c
index fffa839..7fd4ead 100644 (file)
--- a/gst/gstinfo.c
+++ b/gst/gstinfo.c
@@ -2906,9 +2906,7 @@ gst_debug_get_stack_trace (GstStackTraceFlags flags)
 #ifdef HAVE_UNWIND
   if ((flags & GST_STACK_TRACE_SHOW_FULL) || !have_backtrace)
     trace = generate_unwind_trace (flags);
-#endif /* HAVE_UNWIND */
-
-#ifdef HAVE_DBGHELP
+#elif defined(HAVE_DBGHELP)
   trace = generate_dbghelp_trace ();
 #endif
 

diff --git a/meson.build b/meson.build
index db63f66..f2386de 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -350,19 +350,32 @@ unwind_dep = dependency('libunwind', required : get_option('libunwind'))
 dw_dep = dependency('libdw', required: get_option('libdw'))
 dbghelp_dep = dependency('DbgHelp', required : get_option('dbghelp'))
 backtrace_deps = [unwind_dep, dw_dep, dbghelp_dep]
-if unwind_dep.found()
+backtrace_source_info = false
+backtrace_minimal = false
+# MSVC debug stack trace support
+if host_system == 'windows' and dbghelp_dep.found()
+  cdata.set('HAVE_DBGHELP', 1)
+  backtrace_source_info = true
+# DWARF stack trace support with libunwind and elf-utils
+elif unwind_dep.found()
   cdata.set('HAVE_UNWIND', 1)
   if dw_dep.found()
     cdata.set('HAVE_DW', 1)
-  else
-    message('Support for backtraces is partial only.')
+    backtrace_source_info = true
   endif
+  backtrace_minimal = true
+# Basic backtrace() stack trace support
 elif cc.has_function('backtrace')
   cdata.set('HAVE_BACKTRACE', 1)
-elif dbghelp_dep.found()
-  cdata.set('HAVE_DBGHELP', 1)
-else
-  message('NO backtraces support.')
+  backtrace_minimal = true
+endif
+# Print messages about what was enabled
+if not backtrace_source_info
+  if not backtrace_minimal
+    message('NO support for stack traces.')
+  else
+    message('Minimal support for stack traces, no source info.')
+  endif
 endif
 
 if cc.has_header('execinfo.h')