Bug 1859964 - --enable-phc doesn't always imply --enable-frame-pointers r=glandium

Differential Revision: https://phabricator.services.mozilla.com/D191404

Author: PaulBone

build/moz.configure/memory.configure

@@ -90,13 +90,34 @@ option(
     default=phc_default,
     when="--enable-jemalloc",
     help="{Enable|Disable} PHC (Probabilistic Memory Checker). "
-    "Also enables frame pointers",
+    "Also enables frame pointers when needed",
 )
-imply_option("--enable-frame-pointers", True, when="--enable-phc")
-
 
 set_config("MOZ_PHC", True, when="--enable-phc")
 
+
+# PHC parses stacks using frame pointers on these systems.
+@depends("--enable-phc", target, have_unwind, when="--enable-jemalloc")
+def phc_implies_frame_pointers(phc, target, have_unwind):
+    if not phc:
+        return False
+
+    # This should be kept in sync with the ifdefs in memory/build/PHC.cpp
+    # that control stack walking.
+    # This is true for the first two options in PHC.cpp
+    if (target.os == "WINNT" and target.cpu == "x86") or target.kernel == "Darwin":
+        return True
+
+    # This should match the #defines in mozglue/misc/StackWalk.cpp
+    if (target.cpu in ("x86", "ppc")) and (target.kernel in ("Darwin", "Linux")):
+        return not have_unwind
+
+    return False
+
+
+imply_option("--enable-frame-pointers", True, when=phc_implies_frame_pointers)
+
+
 with only_when(depends(target.os)(lambda os: os != "WINNT")):
     set_define("HAVE_STRNDUP", check_symbol("strndup"))
     set_define("HAVE_POSIX_MEMALIGN", check_symbol("posix_memalign"))

build/moz.configure/toolchain.configure

@@ -2335,6 +2335,7 @@ def ub_unsigned_overflow_san():
 
 add_old_configure_assignment("MOZ_UNSIGNED_OVERFLOW_SANITIZE", ub_unsigned_overflow_san)
 
+
 # Security Hardening
 # ==============================================================
 
@@ -2538,6 +2539,15 @@ def frame_pointer_flags(enable, flags):
 set_config("MOZ_FRAMEPTR_FLAGS", frame_pointer_flags)
 
 
+# Stack unwinding without frame pointers
+# ==============================================================
+
+
+have_unwind = check_symbol(
+    "_Unwind_Backtrace", when=check_header("unwind.h", when=target_is_unix)
+)
+
+
 # Code Coverage
 # ==============================================================
 

js/moz.configure

@@ -1374,10 +1374,7 @@ with only_when(compile_environment & depends(target.os)(lambda os: os != "WINNT"
 
     set_define("MOZ_DEMANGLE_SYMBOLS", demangle_symbols)
 
-    set_define(
-        "HAVE__UNWIND_BACKTRACE",
-        check_symbol("_Unwind_Backtrace", when=check_header("unwind.h")),
-    )
+    set_define("HAVE__UNWIND_BACKTRACE", True, when=have_unwind)
 
 with only_when(compile_environment):
     set_define("HAVE__GETC_NOLOCK", check_symbol("_getc_nolock"))

memory/build/PHC.cpp

@@ -207,6 +207,8 @@ class StackTrace : public phc::StackTrace {
 void StackTrace::Fill() {
   mLength = 0;
 
+// These ifdefs should be kept in sync with the conditions in
+// phc_implies_frame_pointers in build/moz.configure/memory.configure
 #if defined(XP_WIN) && defined(_M_IX86)
   // This avoids MozStackWalk(), which causes unusably slow startup on Win32
   // when it is called during static initialization (see bug 1241684).

mozglue/misc/StackWalk.cpp

@@ -639,6 +639,9 @@ MFBT_API bool MozDescribeCodeAddress(void* aPC,
 }
 
 // i386 or PPC Linux stackwalking code
+//
+// Changes to to OS/Architecture support here should be reflected in
+// build/moz.configure/memory.configure
 #elif HAVE_DLADDR &&                                           \
     (HAVE__UNWIND_BACKTRACE || MOZ_STACKWALK_SUPPORTS_LINUX || \
      MOZ_STACKWALK_SUPPORTS_MACOSX)
@@ -680,6 +683,9 @@ void DemangleSymbol(const char* aSymbol, char* aBuffer, int aBufLen) {
 }  // namespace mozilla
 
 // {x86, ppc} x {Linux, Mac} stackwalking code.
+//
+// Changes to to OS/Architecture support here should be reflected in
+// build/moz.configure/memory.configure
 #  if ((defined(__i386) || defined(PPC) || defined(__ppc__)) && \
        (MOZ_STACKWALK_SUPPORTS_MACOSX || MOZ_STACKWALK_SUPPORTS_LINUX))