stdenv: make -nostdinc work as intended

Right now we add glibc to search path also -nostdinc was provided,
which breaks projects providing their own gcc.

pkgs/applications/networking/browsers/firefox/common.nix

@@ -177,7 +177,8 @@ stdenv.mkDerivation ({
     # included we need to look in a few places.
     # TODO: generalize this process for other use-cases.
 
-    BINDGEN_CFLAGS="$(< ${stdenv.cc}/nix-support/libc-cflags) \
+    BINDGEN_CFLAGS="$(< ${stdenv.cc}/nix-support/libc-crt1-cflags) \
+      $(< ${stdenv.cc}/nix-support/libc-cflags) \
       $(< ${stdenv.cc}/nix-support/cc-cflags) \
       $(< ${stdenv.cc}/nix-support/libcxx-cxxflags) \
       ${lib.optionalString stdenv.cc.isClang "-idirafter ${stdenv.cc.cc}/lib/clang/${lib.getVersion stdenv.cc.cc}/include"} \

pkgs/applications/networking/mailreaders/thunderbird/default.nix

@@ -175,7 +175,8 @@ stdenv.mkDerivation rec {
     # included we need to look in a few places.
     # TODO: generalize this process for other use-cases.
 
-    BINDGEN_CFLAGS="$(< ${stdenv.cc}/nix-support/libc-cflags) \
+    BINDGEN_CFLAGS="$(< ${stdenv.cc}/nix-support/libc-crt1-cflags) \
+      $(< ${stdenv.cc}/nix-support/libc-cflags) \
       $(< ${stdenv.cc}/nix-support/cc-cflags) \
       $(< ${stdenv.cc}/nix-support/libcxx-cxxflags) \
       ${

pkgs/build-support/cc-wrapper/add-flags.sh

@@ -33,10 +33,14 @@ NIX_CFLAGS_COMPILE_@suffixSalt@="-B@out@/bin/ $NIX_CFLAGS_COMPILE_@suffixSalt@"
 # Export and assign separately in order that a failing $(..) will fail
 # the script.
 
-if [ -e @out@/nix-support/libc-cflags ]; then
+if [[ "$cInclude" = 1 ]] && [ -e @out@/nix-support/libc-cflags ]; then
     NIX_CFLAGS_COMPILE_@suffixSalt@="$(< @out@/nix-support/libc-cflags) $NIX_CFLAGS_COMPILE_@suffixSalt@"
 fi
 
+if [ -e @out@/nix-support/libc-crt1-cflags ]; then
+    NIX_CFLAGS_COMPILE_@suffixSalt@="$(< @out@/nix-support/libc-crt1-cflags) $NIX_CFLAGS_COMPILE_@suffixSalt@"
+fi
+
 if [ -e @out@/nix-support/libcxx-cxxflags ]; then
     NIX_CXXSTDLIB_COMPILE_@suffixSalt@+=" $(< @out@/nix-support/libcxx-cxxflags)"
 fi

pkgs/build-support/cc-wrapper/cc-wrapper.sh

@@ -17,16 +17,6 @@ fi
 
 source @out@/nix-support/utils.bash
 
-# Flirting with a layer violation here.
-if [ -z "${NIX_BINTOOLS_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
-    source @bintools@/nix-support/add-flags.sh
-fi
-
-# Put this one second so libc ldflags take priority.
-if [ -z "${NIX_CC_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
-    source @out@/nix-support/add-flags.sh
-fi
-
 
 # Parse command line options and set several variables.
 # For instance, figure out if linker flags should be passed.
@@ -37,6 +27,7 @@ cc1=0
 # shellcheck disable=SC2193
 [[ "@prog@" = *++ ]] && isCpp=1 || isCpp=0
 cppInclude=1
+cInclude=1
 
 expandResponseParams "$@"
 declare -i n=0
@@ -63,6 +54,7 @@ while (( "$n" < "$nParams" )); do
     elif [ "$p" = -nostdlib ]; then
         isCpp=-1
     elif [ "$p" = -nostdinc ]; then
+        cInclude=0
         cppInclude=0
     elif [ "$p" = -nostdinc++ ]; then
         cppInclude=0
@@ -111,6 +103,15 @@ if [[ "${NIX_ENFORCE_PURITY:-}" = 1 && -n "$NIX_STORE" ]]; then
     params=(${rest+"${rest[@]}"})
 fi
 
+# Flirting with a layer violation here.
+if [ -z "${NIX_BINTOOLS_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
+    source @bintools@/nix-support/add-flags.sh
+fi
+
+# Put this one second so libc ldflags take priority.
+if [ -z "${NIX_CC_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
+    source @out@/nix-support/add-flags.sh
+fi
 
 # Clear march/mtune=native -- they bring impurity.
 if [ "$NIX_ENFORCE_NO_NATIVE_@suffixSalt@" = 1 ]; then

pkgs/build-support/cc-wrapper/default.nix

@@ -287,7 +287,7 @@ stdenv.mkDerivation {
     + optionalString (libc != null) (''
       touch "$out/nix-support/libc-cflags"
       touch "$out/nix-support/libc-ldflags"
-      echo "-B${libc_lib}${libc.libdir or "/lib/"}" >> $out/nix-support/libc-cflags
+      echo "-B${libc_lib}${libc.libdir or "/lib/"}" >> $out/nix-support/libc-crt1-cflags
     '' + optionalString (!(cc.langD or false)) ''
       echo "-idirafter ${libc_dev}${libc.incdir or "/include"}" >> $out/nix-support/libc-cflags
     '' + optionalString (isGNU && (!(cc.langD or false))) ''
@@ -429,7 +429,7 @@ stdenv.mkDerivation {
 
     + optionalString (libc != null && targetPlatform.isAvr) ''
       for isa in avr5 avr3 avr4 avr6 avr25 avr31 avr35 avr51 avrxmega2 avrxmega4 avrxmega5 avrxmega6 avrxmega7 tiny-stack; do
-        echo "-B${getLib libc}/avr/lib/$isa" >> $out/nix-support/libc-cflags
+        echo "-B${getLib libc}/avr/lib/$isa" >> $out/nix-support/libc-crt1-cflags
       done
     ''
 

pkgs/development/compilers/gcc/builder.sh

@@ -61,7 +61,7 @@ if test "$noSysDirs" = "1"; then
         if [[ -e "${!curCC}/nix-support/orig-libc" ]]; then
             # Figure out what extra compiling flags to pass to the gcc compilers
             # being generated to make sure that they use our libc.
-            extraFlags=($(< "${!curCC}/nix-support/libc-cflags"))
+            extraFlags=($(< "${!curCC}/nix-support/libc-crt1-cflags") $(< "${!curCC}/nix-support/libc-cflags"))
 
             # The path to the Libc headers
             libc_devdir="$(< "${!curCC}/nix-support/orig-libc-dev")"

pkgs/development/libraries/gcc/libstdc++/5.nix

@@ -62,7 +62,7 @@ stdenv.mkDerivation rec {
 
     # Figure out what extra flags to pass to the gcc compilers
     # being generated to make sure that they use our glibc.
-    EXTRA_FLAGS="-I$NIX_FIXINC_DUMMY $(cat $NIX_CC/nix-support/libc-cflags) -O2"
+    EXTRA_FLAGS="-I$NIX_FIXINC_DUMMY $(cat $NIX_CC/nix-support/libc-crt1-cflags) $(cat $NIX_CC/nix-support/libc-cflags) -O2"
 
     extraLDFlags="-L$glibc_libdir -rpath $glibc_libdir $(cat $NIX_BINTOOLS/nix-support/libc-ldflags) $(cat $NIX_BINTOOLS/nix-support/libc-ldflags-before)"
     for i in $extraLDFlags; do

pkgs/test/cc-wrapper/default.nix

@@ -45,6 +45,14 @@ in stdenv.mkDerivation {
     NIX_LDFLAGS="-L$NIX_BUILD_TOP/foo/lib -rpath $NIX_BUILD_TOP/foo/lib" $CC -lfoo -o ldflags-check ${./ldflags-main.c}
     ./ldflags-check
 
+    printf "Check whether -nostdinc and -nostdinc++ is handled correctly" >&2
+    mkdir -p std-include
+    cp ${./stdio.h} std-include/stdio.h
+    NIX_DEBUG=1 $CC -I std-include -nostdinc -o nostdinc-main ${./nostdinc-main.c}
+    ./nostdinc-main
+    $CXX -I std-include -nostdinc++ -o nostdinc-main++ ${./nostdinc-main.c}
+    ./nostdinc-main++
+
     ${optionalString sanitizersWorking ''
       printf "checking whether sanitizers are fully functional... ">&2
       $CC -o sanitizers -fsanitize=address,undefined ${./sanitizers.c}

pkgs/test/cc-wrapper/nostdinc-main.c

@@ -0,0 +1,8 @@
+// This one should not come from libc because of -nostdinc
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+  // provided by our own stdio.h
+  foo();
+  return 0;
+}

pkgs/test/cc-wrapper/stdio.h

@@ -0,0 +1 @@
+static void foo(void) {}