cc-wrapper: Fix standalone gcc

This ensures that all salted variables are defined even if the wrapped program
is invoked outside nix-build environment.

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

···
 # that case, it is cheaper/better to not repeat this step and let the forked
 # wrapped binary just inherit the work of the forker's wrapper script.
 
-# Accumulate prefixes for taking in the right input parameters. See setup-hook
+var_templates=(
+    NIX_CC_WRAPPER+START_HOOK
+    NIX_CC_WRAPPER+EXEC_HOOK
+    NIX_LD_WRAPPER+START_HOOK
+    NIX_LD_WRAPPER+EXEC_HOOK
+
+    NIX+CFLAGS_COMPILE
+    NIX+CFLAGS_LINK
+    NIX+CXXSTDLIB_COMPILE
+    NIX+CXXSTDLIB_LINK
+    NIX+GNATFLAGS_COMPILE
+    NIX+IGNORE_LD_THROUGH_GCC
+    NIX+LDFLAGS
+    NIX+LDFLAGS_BEFORE
+    NIX+LDFLAGS_AFTER
+    NIX+LDFLAGS_HARDEN
+
+    NIX+SET_BUILD_ID
+    NIX+DONT_SET_RPATH
+    NIX+ENFORCE_NO_NATIVE
+)
+
+# Accumulate infixes for taking in the right input parameters. See setup-hook
 # for details.
-declare -a role_prefixes=()
-if [[ -n "${NIX_CC_WRAPPER_@infixSalt@_TARGET_BUILD:-}" ]]; then
-    role_prefixes+=(_BUILD)
+declare -a role_infixes=()
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_BUILD:-}" ]; then
+    role_infixes+=(_BUILD_)
 fi
-if [[ -n "${NIX_CC_WRAPPER_@infixSalt@_TARGET_HOST:-}" ]]; then
-    role_prefixes+=('')
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_HOST:-}" ]; then
+    role_infixes+=(_)
 fi
-if [[ -n "${NIX_CC_WRAPPER_@infixSalt@_TARGET_TARGET:-}" ]]; then
-    role_prefixes+=(_TARGET)
+if [ "${NIX_CC_WRAPPER_@infixSalt@_TARGET_TARGET:-}" ]; then
+    role_infixes+=(_TARGET_)
 fi
 
-# For each role we serve, we accumulate the input parameters into our own
-# cc-wrapper-derivation-specific environment variables.
-for pre in "${role_prefixes[@]}"; do
-    # We need to mangle names for hygiene, but also take parameters/overrides
-    # from the environment.
-    slurpUnsalted () {
-        case "$1" in
-            CC_WRAPPER_*)
-                local firstPre=NIX_CC_WRAPPER_
-                local varname="${1#CC_WRAPPER_}"
-                ;;
-            LD_WRAPPER_*)
-                local firstPre=NIX_LD_WRAPPER_
-                local varname="${1#LD_WRAPPER_}"
-                ;;
-            *)
-                local firstPre=NIX_
-                local varname="$1"
-                ;;
-        esac
-        local inputVar="${firstPre}${pre}${varname}"
-        local outputVar="${firstPre}@infixSalt@_${varname}"
-        local delimiter=''
-        if [[ -n "${!outputVar:-}" && -n "${!inputVar:-}" ]]; then
-            delimiter=' '
+# We need to mangle names for hygiene, but also take parameters/overrides
+# from the environment.
+for var in "${var_templates[@]}"; do
+    outputVar="${var/+/_@infixSalt@_}"
+    export ${outputVar}+=''
+    # For each role we serve, we accumulate the input parameters into our own
+    # cc-wrapper-derivation-specific environment variables.
+    for infix in "${role_infixes[@]}"; do
+        inputVar="${var/+/${infix}}"
+        if [ -v "$inputVar" ]; then
+            export ${outputVar}+="${!outputVar:+ }${!inputVar}"
         fi
-        # Easiest to just do this to deal with either the input or (old) output.
-        set +u
-        export ${outputVar}+="${delimiter}${!inputVar}"
-        set -u
-    }
-
-    slurpUnsalted CC_WRAPPER_START_HOOK
-    slurpUnsalted CC_WRAPPER_EXEC_HOOK
-    slurpUnsalted LD_WRAPPER_START_HOOK
-    slurpUnsalted LD_WRAPPER_EXEC_HOOK
-
-    slurpUnsalted CFLAGS_COMPILE
-    slurpUnsalted CFLAGS_LINK
-    slurpUnsalted CXXSTDLIB_COMPILE
-    slurpUnsalted CXXSTDLIB_LINK
-    slurpUnsalted GNATFLAGS_COMPILE
-    slurpUnsalted IGNORE_LD_THROUGH_GCC
-    slurpUnsalted LDFLAGS
-    slurpUnsalted LDFLAGS_BEFORE
-    slurpUnsalted LDFLAGS_AFTER
-    slurpUnsalted LDFLAGS_HARDEN
-
-    slurpUnsalted SET_BUILD_ID
-    slurpUnsalted DONT_SET_RPATH
-    slurpUnsalted ENFORCE_NO_NATIVE
+    done
 done
-unset -f slurpUnsalted
 
 # `-B@out@/bin' forces cc to use ld-wrapper.sh when calling ld.
-export NIX_@infixSalt@_CFLAGS_COMPILE="-B@out@/bin/ $NIX_@infixSalt@_CFLAGS_COMPILE"
+NIX_@infixSalt@_CFLAGS_COMPILE="-B@out@/bin/ $NIX_@infixSalt@_CFLAGS_COMPILE"
 
 # Export and assign separately in order that a failing $(..) will fail
 # the script.
 
 if [ -e @out@/nix-support/libc-cflags ]; then
-    export NIX_@infixSalt@_CFLAGS_COMPILE
     NIX_@infixSalt@_CFLAGS_COMPILE="$(< @out@/nix-support/libc-cflags) $NIX_@infixSalt@_CFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/cc-cflags ]; then
-    export NIX_@infixSalt@_CFLAGS_COMPILE
     NIX_@infixSalt@_CFLAGS_COMPILE="$(< @out@/nix-support/cc-cflags) $NIX_@infixSalt@_CFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/gnat-cflags ]; then
-    export NIX_@infixSalt@_GNATFLAGS_COMPILE
     NIX_@infixSalt@_GNATFLAGS_COMPILE="$(< @out@/nix-support/gnat-cflags) $NIX_@infixSalt@_GNATFLAGS_COMPILE"
 fi
 
 if [ -e @out@/nix-support/libc-ldflags ]; then
-    export NIX_@infixSalt@_LDFLAGS
     NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/libc-ldflags)"
 fi
 
 if [ -e @out@/nix-support/cc-ldflags ]; then
-    export NIX_@infixSalt@_LDFLAGS
     NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/cc-ldflags)"
 fi
 
 if [ -e @out@/nix-support/libc-ldflags-before ]; then
-    export NIX_@infixSalt@_LDFLAGS_BEFORE
     NIX_@infixSalt@_LDFLAGS_BEFORE="$(< @out@/nix-support/libc-ldflags-before) $NIX_@infixSalt@_LDFLAGS_BEFORE"
 fi
 
-# That way forked processes don't againt extend these environment variables
+# That way forked processes will not extend these environment variables again.
 export NIX_CC_WRAPPER_@infixSalt@_FLAGS_SET=1