commit 861ffb371c66fbb7a041158dab0d7b5b0f7ba8e0
Author: Panu Matilainen <pmatilai@redhat.com>
Date:   Fri Mar 23 14:08:21 2018 +0200

    Add support for nested Lua macro expansion (RhBug:490740)
    - Lift the printbuffer accounting out of rpmlua into a struct of
      its own (Funny thing, this looks a whole lot like the macro
      expansion buffer and Good Ole StringBuf Brothers ... Boys ... Mam.
      Unify them one of these days maybe)
    - Replace the simplistic on/off printbuffer with a stack of buffers,
      fixup the lone caller to use the new internal push/pop API.
    
    Backported from commit ecfece7ec0d0eb0485745568d10dabc428e92824

diff --git a/rpmio/macro.c b/rpmio/macro.c
index 11e23a3..c150a28 100644
--- a/rpmio/macro.c
+++ b/rpmio/macro.c
@@ -1229,13 +1229,13 @@ expandMacro(MacroBuf mb)
 		const char *ls = s+sizeof("{lua:")-1;
 		const char *lse = se-sizeof("}")+1;
 		char *scriptbuf = (char *)xmalloc((lse-ls)+1);
-		const char *printbuf;
+		char *printbuf;
 		memcpy(scriptbuf, ls, lse-ls);
 		scriptbuf[lse-ls] = '\0';
-		rpmluaSetPrintBuffer(lua, 1);
+		rpmluaPushPrintBuffer(lua);
 		if (rpmluaRunScript(lua, scriptbuf, NULL) == -1)
 		    rc = 1;
-		printbuf = rpmluaGetPrintBuffer(lua);
+		printbuf = rpmluaPopPrintBuffer(lua);
 		if (printbuf) {
 		    size_t len = strlen(printbuf);
 		    if (len > mb->nb)
@@ -1243,8 +1243,8 @@ expandMacro(MacroBuf mb)
 		    memcpy(mb->t, printbuf, len);
 		    mb->t += len;
 		    mb->nb -= len;
+		    free(printbuf);
 		}
-		rpmluaSetPrintBuffer(lua, 0);
 		free(scriptbuf);
 		s = se;
 		continue;
diff --git a/rpmio/rpmlua.c b/rpmio/rpmlua.c
index bd94eff..c6e8254 100644
--- a/rpmio/rpmlua.c
+++ b/rpmio/rpmlua.c
@@ -31,6 +31,13 @@
 			\
 	    )
 
+struct rpmluapb_s {
+    size_t alloced;
+    size_t used;
+    char *buf;
+    rpmluapb next;
+};
+
 static rpmlua globalLuaState = NULL;
 
 static int luaopen_rpm(lua_State *L);
@@ -123,20 +130,31 @@ void *rpmluaGetData(rpmlua _lua, const char *key)
     return getdata(lua->L, key);
 }
 
-void rpmluaSetPrintBuffer(rpmlua _lua, int flag)
+void rpmluaPushPrintBuffer(rpmlua _lua)
 {
     INITSTATE(_lua, lua);
-    lua->storeprint = flag;
-    free(lua->printbuf);
-    lua->printbuf = NULL;
-    lua->printbufsize = 0;
-    lua->printbufused = 0;
+    rpmluapb prbuf = xcalloc(1, sizeof(*prbuf));
+    prbuf->buf = NULL;
+    prbuf->alloced = 0;
+    prbuf->used = 0;
+    prbuf->next = lua->printbuf;
+
+    lua->printbuf = prbuf;
 }
 
-const char *rpmluaGetPrintBuffer(rpmlua _lua)
+char *rpmluaPopPrintBuffer(rpmlua _lua)
 {
     INITSTATE(_lua, lua);
-    return lua->printbuf;
+    rpmluapb prbuf = lua->printbuf;
+    char *ret = NULL;
+
+    if (prbuf) {
+	ret = prbuf->buf;
+	lua->printbuf = prbuf->next;
+	free(prbuf);
+    }
+    
+    return ret;
 }
 
 static int pushvar(lua_State *L, rpmluavType type, void *value)
@@ -770,16 +788,17 @@ static int rpm_print (lua_State *L)
 	s = lua_tostring(L, -1);  /* get result */
 	if (s == NULL)
 	    return luaL_error(L, "`tostring' must return a string to `print'");
-	if (lua->storeprint) {
+	if (lua->printbuf) {
+	    rpmluapb prbuf = lua->printbuf;
 	    int sl = lua_strlen(L, -1);
-	    if (lua->printbufused+sl+1 > lua->printbufsize) {
-		lua->printbufsize += sl+512;
-		lua->printbuf = xrealloc(lua->printbuf, lua->printbufsize);
+	    if (prbuf->used+sl+1 > prbuf->alloced) {
+		prbuf->alloced += sl+512;
+		prbuf->buf = xrealloc(prbuf->buf, prbuf->alloced);
 	    }
 	    if (i > 1)
-		lua->printbuf[lua->printbufused++] = '\t';
-	    memcpy(lua->printbuf+lua->printbufused, s, sl+1);
-	    lua->printbufused += sl;
+		prbuf->buf[prbuf->used++] = '\t';
+	    memcpy(prbuf->buf+prbuf->used, s, sl+1);
+	    prbuf->used += sl;
 	} else {
 	    if (i > 1)
 		(void) fputs("\t", stdout);
@@ -787,14 +806,15 @@ static int rpm_print (lua_State *L)
 	}
 	lua_pop(L, 1);  /* pop result */
     }
-    if (!lua->storeprint) {
+    if (!lua->printbuf) {
 	(void) fputs("\n", stdout);
     } else {
-	if (lua->printbufused+1 > lua->printbufsize) {
-	    lua->printbufsize += 512;
-	    lua->printbuf = xrealloc(lua->printbuf, lua->printbufsize);
+	rpmluapb prbuf = lua->printbuf;
+	if (prbuf->used+1 > prbuf->alloced) {
+	    prbuf->alloced += 512;
+	    prbuf->buf = xrealloc(prbuf->buf, prbuf->alloced);
 	}
-	lua->printbuf[lua->printbufused] = '\0';
+	prbuf->buf[prbuf->used] = '\0';
     }
     return 0;
 }
diff --git a/rpmio/rpmlua.h b/rpmio/rpmlua.h
index 12b0fa1..ab6bd3c 100644
--- a/rpmio/rpmlua.h
+++ b/rpmio/rpmlua.h
@@ -12,13 +12,12 @@ typedef enum rpmluavType_e {
 #include <stdarg.h>
 #include <lua.h>
 
+typedef struct rpmluapb_s * rpmluapb;
+
 struct rpmlua_s {
     lua_State *L;
     size_t pushsize;
-    int storeprint;
-    size_t printbufsize;
-    size_t printbufused;
-    char *printbuf;
+    rpmluapb printbuf;
 };
 
 struct rpmluav_s {
@@ -56,8 +55,8 @@ void rpmluaInteractive(rpmlua lua);
 void *rpmluaGetData(rpmlua lua, const char *key);
 void rpmluaSetData(rpmlua lua, const char *key, const void *data);
 
-const char *rpmluaGetPrintBuffer(rpmlua lua);
-void rpmluaSetPrintBuffer(rpmlua lua, int flag);
+char *rpmluaPopPrintBuffer(rpmlua lua);
+void rpmluaPushPrintBuffer(rpmlua lua);
 
 void rpmluaGetVar(rpmlua lua, rpmluav var);
 void rpmluaSetVar(rpmlua lua, rpmluav var);