Handle missing or empty object file from compiler properly

NEWS

@@ -49,6 +49,10 @@ New features and improvements:
   - Standard error output from the compiler is now only stored in the cache if
     it's non-empty.
 
+  - If the compiler produces no object file or an empty object file, but gives
+    a zero exit status (could be due to a file system problem, a buggy program
+    specified by CCACHE_PREFIX, etc.), ccache copes with it properly.
+
   - Added installcheck and distcheck make targets.
 
   - Clarified cache size limit options' semantics

ccache.c

@@ -546,6 +546,17 @@ static void to_cache(ARGS *args)
 		failed();
 	}
 
+	if (stat(tmp_obj, &st) != 0) {
+		cc_log("The compiler didn't produce an object file");
+		stats_update(STATS_NOOUTPUT);
+		failed();
+	}
+	if (st.st_size == 0) {
+		cc_log("The compiler produced an empty object file");
+		stats_update(STATS_EMPTYOUTPUT);
+		failed();
+	}
+
 	compress = !getenv("CCACHE_NOCOMPRESS");
 
 	if (stat(tmp_stderr, &st) != 0) {

ccache.h

@@ -43,6 +43,8 @@ enum stats {
 	STATS_UNSUPPORTED,
 	STATS_OUTSTDOUT,
 	STATS_CACHEHIT_DIR,
+	STATS_NOOUTPUT,
+	STATS_EMPTYOUTPUT,
 
 	STATS_END
 };

stats.c

@@ -54,6 +54,8 @@ static struct {
 	{ STATS_LINK,         "called for link                ", NULL, 0 },
 	{ STATS_MULTIPLE,     "multiple source files          ", NULL, 0 },
 	{ STATS_STDOUT,       "compiler produced stdout       ", NULL, 0 },
+	{ STATS_NOOUTPUT,     "compiler produced no output    ", NULL, 0 },
+	{ STATS_EMPTYOUTPUT,  "compiler produced empty output ", NULL, 0 },
 	{ STATS_STATUS,       "compile failed                 ", NULL, 0 },
 	{ STATS_ERROR,        "ccache internal error          ", NULL, 0 },
 	{ STATS_PREPROCESSOR, "preprocessor error             ", NULL, 0 },

test.sh

@@ -275,6 +275,33 @@ base_tests() {
     checkstat 'cache hit (preprocessed)' 11
     checkstat 'cache miss' 39
 
+    testname="no object file"
+    cat <<'EOF' >test_no_obj.c
+int test_no_obj;
+EOF
+    cat <<'EOF' >prefix-remove.sh
+#!/bin/sh
+echo "$*" >>/tmp/foo
+"$@"
+[ x$3 = x-o ] && rm $4
+EOF
+    chmod +x prefix-remove.sh
+    CCACHE_PREFIX=$PWD/prefix-remove.sh $CCACHE_COMPILE -c test_no_obj.c
+    checkstat 'compiler produced no output' 1
+
+    testname="empty object file"
+    cat <<'EOF' >test_empty_obj.c
+int test_empty_obj;
+EOF
+    cat <<'EOF' >prefix-empty.sh
+#!/bin/sh
+"$@"
+[ x$3 = x-o ] && cp /dev/null $4
+EOF
+    chmod +x prefix-empty.sh
+    CCACHE_PREFIX=$PWD/prefix-empty.sh $CCACHE_COMPILE -c test_empty_obj.c
+    checkstat 'compiler produced empty output' 1
+
     testname="stderr-files"
     num=`find $CCACHE_DIR -name '*.stderr' | wc -l`
     if [ $num -ne 0 ]; then