test.bash, crossbuild: catch MacOS test build failures

Regression test for https://github.com/rfjakob/gocryptfs/issues/623

Fixes https://github.com/rfjakob/gocryptfs/issues/623

crossbuild.bash

@@ -7,9 +7,13 @@ function build {
 	go build -tags without_openssl -o /dev/null
 }
 
-set -eux
+function compile_tests {
+	for i in $(go list ./...) ; do
+		go test -c -tags without_openssl -o /dev/null "$i" > /dev/null
+	done
+}
 
-cd "$(dirname "$0")"
+set -eux
 
 export GO111MODULE=on
 export CGO_ENABLED=0
@@ -22,6 +26,8 @@ GOOS=linux  GOARCH=arm64         build
 
 # MacOS on Intel
 GOOS=darwin GOARCH=amd64 build
+# Catch tests that don't work on MacOS (takes a long time so we only run it once)
+time GOOS=darwin GOARCH=amd64 compile_tests
 
 # MacOS on Apple Silicon M1.
 # Go 1.16 added support for the M1 and added ios/arm64,

test.bash

@@ -93,4 +93,12 @@ if find . -type f -name \*.go -print0 | xargs -0 grep -E 'syscall.(Setegid|Seteu
 	exit 1
 fi
 
+if find . -type f -name \*.go -print0 | xargs -0 grep '\.Creat('; then
+	# MacOS does not have syscall.Creat(). Creat() is equivalent to Open(..., O_CREAT|O_WRONLY|O_TRUNC, ...),
+	# but usually you want O_EXCL instead of O_TRUNC because it is safer, so that's what we suggest
+	# instead.
+	echo "$MYNAME: Please use Open(..., O_CREAT|O_WRONLY|O_EXCL, ...) instead of Creat()! https://github.com/rfjakob/gocryptfs/issues/623"
+	exit 1
+fi
+
 ) 200> "$LOCKFILE"