diff --git a/.gitignore b/.gitignore
index 03dfbb3..0f7ad73 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@
 /include/
 /templates/
 /configure/*.local
+/configure/CONFIG_SITE.Common.*
 O.*/
 *.orig
 *.log
diff --git a/configure/CONFIG_SITE b/configure/CONFIG_SITE
index 3fb5197..7ab42d8 100644
--- a/configure/CONFIG_SITE
+++ b/configure/CONFIG_SITE
@@ -43,7 +43,3 @@ CHECK_RELEASE = YES
 
 # MSVC - skip defining min()/max() macros and enable APIs
 USR_CPPFLAGS_WIN32 += -DNOMINMAX -D_WIN32_WINNT=_WIN32_WINNT_VISTA
-
-ifneq ($(filter-out msvc,$(CMPLR_CLASS)),)
-USR_CXXFLAGS += -std=c++11
-endif
diff --git a/configure/Makefile b/configure/Makefile
index c8652b6..19aebd4 100644
--- a/configure/Makefile
+++ b/configure/Makefile
@@ -8,3 +8,18 @@ CONFIGS += $(subst ../,,$(wildcard $(CONFIG_INSTALLS)))
 CFG += CONFIG_PVXS_VERSION
 
 include $(TOP)/configure/RULES
+
+ifdef T_A
+install: $(TOP)/configure/CONFIG_SITE.Common.$(T_A)
+
+$(TOP)/configure/CONFIG_SITE.Common.$(T_A): toolchain.c
+	$(PREPROCESS.cpp)
+
+else
+clean: cleanToolchain
+
+.PHONY: cleanToolchain
+cleanToolchain:
+	$(RM) $(wildcard CONFIG_SITE.Common.*)
+
+endif
diff --git a/configure/toolchain.c b/configure/toolchain.c
new file mode 100644
index 0000000..f6faece
--- /dev/null
+++ b/configure/toolchain.c
@@ -0,0 +1,37 @@
+/* Compiler inspection
+ *
+ * expanded as configure/CONFIG_SITE.Common.*
+ */
+#define VERSION_INT(V,R,M,P) ( ((V)<<24) | ((R)<<16) | ((M)<<8) | (P))
+
+CONFIG_LOADED=YES
+
+#if __GNUC__
+/* also true for clang */
+GNUISH=YES
+USR_CXXFLAGS += -std=c++11
+#endif
+
+#if __GNUC__ && !__clang__
+#define GCC_VERSION VERSION_INT(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__, 0)
+
+/* LTO takes a nice chunk out of the .so text size, but blows up the .a size */
+#if GCC_VERSION>=VERSION_INT(4,9,0,0)
+OPT_CFLAGS_YES += -flto
+OPT_CXXFLAGS_YES += -flto
+USR_LDFLAGS += -flto
+#endif
+
+/* Compress debug information on ELF targets for ~25%-50% reduction in .so and .a file size
+ * (C++ debug info is Huuuge!)
+ */
+#if __ELF__ && GCC_VERSION>=VERSION_INT(5,0,0,0)
+USR_CFLAGS += -gz=zlib
+USR_CXXFLAGS += -gz=zlib
+/* Actually a binutils feature, which we can't detect.
+ * Assume binutils upgrade follow gcc
+ */
+USR_LDFLAGS += -Wl,--compress-debug-sections=zlib
+#endif
+
+#endif /* __GNUC__ */
diff --git a/src/Makefile b/src/Makefile
index 9d448fd..a4cee2a 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -7,28 +7,22 @@ include $(TOP)/configure/CONFIG
 
 USR_CPPFLAGS += -DPVXS_API_BUILDING
 
-ifneq (,$(filter gcc clang,$(CMPLR_CLASS)))
+ifdef T_A
+ifneq ($(CONFIG_LOADED),YES)
+$(error Toolchain inspection failed $(MAKEFILE_LIST))
+endif
+endif
 
+ifeq ($(GNUISH),YES)
 # we explicitly mark dllimport/export anyway.
 # So hide our internal symbols to speed up linking/loading on all targets.
 USR_CFLAGS += -fvisibility=hidden
 USR_CXXFLAGS += -fvisibility=hidden -fvisibility-inlines-hidden
-
-# Compress debug information on ELF targets for ~25%-50% reduction in .so and .a file size
-# (C++ debug info is Huuuge!)
-#USR_CFLAGS_Linux += -gz=zlib
-#USR_CXXFLAGS_Linux += -gz=zlib
-#USR_LDFLAGS_Linux += -Wl,--compress-debug-sections=zlib
-
-# LTO takes a nice chunk out of the .so text size, but blows up the .a size
-#USR_CXXFLAGS += -flto
-#USR_LDFLAGS += -flto
+endif
 
 # fault on any undefined symbols (eg. from missing LIB_SYS_LIBS)
 # breaks on older ncurses (circa RHEL6) not using the INPUT() trick to pull in libtinfo.so
-USR_LDFLAGS_Linux += -Wl,--no-undefined -Wl,--no-allow-shlib-undefined
-
-endif
+#USR_LDFLAGS_Linux += -Wl,--no-undefined -Wl,--no-allow-shlib-undefined
 
 EXPANDVARS += PVXS_MAJOR_VERSION
 EXPANDVARS += PVXS_MINOR_VERSION