fix gcc-8.1 build issue on Fedora

Author: kevinushey

src/Makevars.in

@@ -34,8 +34,14 @@ else
   endif
 
   MAKE += -e
-  MAKE_CMD = CONLY="@CC@" CPLUS="@CXX11@" CXXFLAGS="@CXX11FLAGS@ -DTBB_NO_LEGACY=1" PIC_KEY="@CXX11PICFLAGS@" WARNING_SUPPRESS="" $(MAKE)
-  
+  MAKE_CMD =                                  \
+    CONLY="@CC@"                              \
+    CPLUS="@CXX11@"                           \
+    CXXFLAGS="@CXX11FLAGS@ -DTBB_NO_LEGACY=1" \
+    PIC_KEY="@CXX11PICFLAGS@"                 \
+    WARNING_SUPPRESS=""                       \
+    $(MAKE)
+
 endif
 
 ifdef USE_TBB

tools/config/configure.R

@@ -12,6 +12,16 @@ for (candidate in candidates) {
    }
 }
 
+# work around issue with '-Werror=format-security' being specified without
+# a prior '-Wformat', which makes gcc angry
+cxxflags <- read_r_config(sprintf("%sFLAGS", cxx), envir = NULL)[[1]]
+broken <-
+   grepl(" -Werror=format-security ", cxxflags) &&
+   !grepl(" -Wformat ", cxxflags)
+
+if (broken)
+   cxxflags <- gsub("-Werror=format-security", "-Wformat -Werror=format-security", cxxflags)
+
 # define the set of flags appropriate to the current
 # configuration of R
 switch(
@@ -20,23 +30,23 @@ switch(
    CXX11 = define(
       CC            = "$(CC)",
       CXX11         = "$(CXX11)",
-      CXX11FLAGS    = "$(CXX11FLAGS)",
+      CXX11FLAGS    = cxxflags,
       CXX11STD      = "$(CXX11STD)",
       CXX11PICFLAGS = "$(CXX11PICFLAGS)"
    ),
 
    CXX1X = define(
       CC            = "$(CC)",
       CXX11         = "$(CXX1X)",
-      CXX11FLAGS    = "$(CXX1XFLAGS)",
+      CXX11FLAGS    = cxxflags,
       CXX11STD      = "$(CXX1XSTD)",
       CXX11PICFLAGS = "$(CXX1XPICFLAGS)"
    ),
 
    CXX = define(
       CC            = "$(CC)",
       CXX11         = "$(CXX)",
-      CXX11FLAGS    = "$(CXXFLAGS)",
+      CXX11FLAGS    = cxxflags,
       CXX11STD      = "-std=c++0x",
       CXX11PICFLAGS = "-fPIC"
    ),