diff --git a/build/unix/elfhack/test.c b/build/unix/elfhack/test.c
index bbeebd444da..50cc750264d 100644
--- a/build/unix/elfhack/test.c
+++ b/build/unix/elfhack/test.c
@@ -79,6 +79,7 @@ DEF(several)
 DEF(times)
 
 #else
+#pragma GCC visibility push(default)
 #include <stdlib.h>
 #include <stdio.h>
 
@@ -109,7 +110,7 @@ const char *strings2[] = {
 
 static int ret = 1;
 
-__attribute__((visibility("default"))) int print_status() {
+int print_status() {
     fprintf(stderr, "%s\n", ret ? "FAIL" : "PASS");
     return ret;
 }
@@ -149,4 +150,5 @@ __attribute__((constructor)) void test() {
     end_test();
 }
 
+#pragma GCC visibility pop
 #endif
diff --git a/configure.in b/configure.in
index a9ee5aa9bd2..fcbdb08ac21 100644
--- a/configure.in
+++ b/configure.in
@@ -551,6 +551,20 @@ if test "$GXX" = yes; then
    fi
 fi
 
+CLANG_CC=
+CLANG_CXX=
+if test "$GCC" = yes; then
+   if test "`$CC -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CC=1
+   fi
+fi
+
+if test "$GXX" = yes; then
+   if test "`$CXX -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CXX=1
+   fi
+fi
+
 dnl ========================================================
 dnl Special win32 checks
 dnl ========================================================
@@ -921,6 +935,8 @@ AC_SUBST(GNU_CC)
 AC_SUBST(GNU_CXX)
 AC_SUBST(INTEL_CC)
 AC_SUBST(INTEL_CXX)
+AC_SUBST(CLANG_CC)
+AC_SUBST(CLANG_CXX)
 
 AC_SUBST(STL_FLAGS)
 AC_SUBST(WRAP_STL_INCLUDES)
@@ -1549,8 +1565,8 @@ if test "$GNU_CC"; then
     # -Wbad-function-cast - warns when casting a function to a new return type
     # -Wshadow - removed because it generates more noise than help --pete
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -W -Wno-unused -Wpointer-arith -Wdeclaration-after-statement"
-    if test -z "$INTEL_CC"; then
-       # Don't use -Wcast-align with ICC
+    if test -z "$INTEL_CC" -a -z "$CLANG_CC"; then
+       # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
@@ -1599,8 +1615,8 @@ if test "$GNU_CXX"; then
     CXXFLAGS="$CXXFLAGS -fno-strict-aliasing"
     # Turn on GNU specific features
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor"
-    if test -z "$INTEL_CC"; then
-       # Don't use -Wcast-align with ICC
+    if test -z "$INTEL_CXX" -a -z "$CLANG_CXX"; then
+       # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
diff --git a/js/src/configure.in b/js/src/configure.in
index e8c03b1086e..a685f279d6b 100644
--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -591,6 +591,20 @@ if test "$GXX" = yes; then
    fi
 fi
 
+CLANG_CC=
+CLANG_CXX=
+if test "$GCC" = yes; then
+   if test "`$CC -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CC=1
+   fi
+fi
+
+if test "$GXX" = yes; then
+   if test "`$CXX -v 2>&1 | grep -c 'clang version'`" != "0"; then
+     CLANG_CXX=1
+   fi
+fi
+
 dnl Special win32 checks
 dnl ========================================================
 WINVER=502
@@ -1537,8 +1551,8 @@ if test "$GNU_CC"; then
     # -Wbad-function-cast - warns when casting a function to a new return type
     # -Wshadow - removed because it generates more noise than help --pete
     _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -W -Wno-unused -Wpointer-arith"
-    if test -z "$INTEL_CC"; then
-       # Don't use -Wcast-align with ICC
+    if test -z "$INTEL_CC" -a -z "$CLANG_CC"; then
+       # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
@@ -1587,8 +1601,8 @@ if test "$GNU_CXX"; then
     CXXFLAGS="$CXXFLAGS -fno-strict-aliasing"
     # Turn on GNU specific features
     _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor"
-    if test -z "$INTEL_CC"; then
-       # Don't use -Wcast-align with ICC
+    if test -z "$INTEL_CXX" -a -z "$CLANG_CXX"; then
+       # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
diff --git a/toolkit/crashreporter/google-breakpad/src/common/dwarf_cu_to_module.cc b/toolkit/crashreporter/google-breakpad/src/common/dwarf_cu_to_module.cc
index 9b5382839bc..732f5b47ef0 100644
--- a/toolkit/crashreporter/google-breakpad/src/common/dwarf_cu_to_module.cc
+++ b/toolkit/crashreporter/google-breakpad/src/common/dwarf_cu_to_module.cc
@@ -850,12 +850,12 @@ void DwarfCUToModule::AssignLinesToFunctions() {
     // about what result we produce in that case, just as long as we don't
     // hang or crash.
     while (func_it != functions->end()
-           && current >= (*func_it)->address
+           && next_transition >= (*func_it)->address
            && !within(**func_it, next_transition))
       func_it++;
     func = (func_it != functions->end()) ? *func_it : NULL;
     while (line_it != lines_.end()
-           && current >= line_it->address
+           && next_transition >= line_it->address
            && !within(*line_it, next_transition))
       line_it++;
     line = (line_it != lines_.end()) ? &*line_it : NULL;