1 files changed, 89 insertions, 0 deletions
diff --git a/build/flags-if.sh b/build/flags-if.sh
new file mode 100755
index 0000000..f7b4f33
--- /dev/null
+++ b/build/flags-if.sh
@@ -0,0 +1,89 @@
+#!/bin/sh
+
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Add flags to a makefile if a build succeeds.  Source files can specify their
+# own flags with lines like
+#
+#     /// _CFLAGS += -Wmissing-variable-declarations
+#
+# which will be added to the makefile on success, or lines like
+#
+#     /// -Werror
+#
+# which are just used for the current file.  Lines like
+#
+#     /// ---
+#
+# separate groups of flags, to try multiple ways to achieve something, e.g.
+#
+#     /// CFLAGS += -pthread
+#     /// ---
+#     /// LDLIBS += -lpthread
+
+set -eu
+
+# Any new flags we're using
+FLAGS=""
+# Any new makefile lines we're printing
+OUTPUT=""
+
+# Check the existing flags so we don't add duplicates
+OLD_FLAGS=" $XCPPFLAGS $XCFLAGS $XLDFLAGS $XLDLIBS "
+
+add_flag() {
+    case "$1" in
+        -std=*)
+            # Don't overwrite -std=* flags
+            case "$OLD_FLAGS" in
+                *\ -std=*)
+                    return 1
+                    ;;
+            esac
+            ;;
+        *)
+            if [ "${OLD_FLAGS#* $1 }" != "$OLD_FLAGS" ]; then
+                return 1
+            fi
+            ;;
+    esac
+
+    FLAGS="${FLAGS}${FLAGS:+ }$1"
+}
+
+try_cc() {
+    build/cc.sh "$@" $FLAGS || return $?
+    printf '%s' "$OUTPUT"
+    exit
+}
+
+while IFS="" read -r line; do
+    case "$line" in
+        "/// "*)
+            line="${line#/// }"
+            ;;
+        *)
+            continue
+            ;;
+    esac
+
+    case "$line" in
+        ---)
+            try_cc "$@" || :
+            FLAGS=
+            OUTPUT=
+            ;;
+        *=*)
+            if add_flag "${line#*= }"; then
+                OUTPUT="${OUTPUT}${line}
+"
+            fi
+            ;;
+        *)
+            add_flag "$line" || :
+            ;;
+    esac
+done <"$1"
+
+try_cc "$@"