3 files changed, 33 insertions, 10 deletions

diff --git a/lauxlib.c b/lauxlib.c
index fec834d3..d742fd27 100644
--- a/lauxlib.c
+++ b/lauxlib.c
@@ -249,11 +249,13 @@ LUALIB_API int luaL_fileresult (lua_State *L, int stat, const char *fname) {
     return 1;
   }
   else {
+    const char *msg;
     luaL_pushfail(L);
+    msg = (en != 0) ? strerror(en) : "(no extra info)";
     if (fname)
-      lua_pushfstring(L, "%s: %s", fname, strerror(en));
+      lua_pushfstring(L, "%s: %s", fname, msg);
     else
-      lua_pushstring(L, strerror(en));
+      lua_pushstring(L, msg);
     lua_pushinteger(L, en);
     return 3;
   }
@@ -750,9 +752,12 @@ static const char *getF (lua_State *L, void *ud, size_t *size) {
 
 
 static int errfile (lua_State *L, const char *what, int fnameindex) {
-  const char *serr = strerror(errno);
+  int err = errno;
   const char *filename = lua_tostring(L, fnameindex) + 1;
-  lua_pushfstring(L, "cannot %s %s: %s", what, filename, serr);
+  if (err != 0)
+    lua_pushfstring(L, "cannot %s %s: %s", what, filename, strerror(err));
+  else
+    lua_pushfstring(L, "cannot %s %s", what, filename);
   lua_remove(L, fnameindex);
   return LUA_ERRFILE;
 }
@@ -805,6 +810,7 @@ LUALIB_API int luaL_loadfilex (lua_State *L, const char *filename,
   }
   else {
     lua_pushfstring(L, "@%s", filename);
+    errno = 0;
     lf.f = fopen(filename, "r");
     if (lf.f == NULL) return errfile(L, "open", fnameindex);
   }
@@ -814,6 +820,7 @@ LUALIB_API int luaL_loadfilex (lua_State *L, const char *filename,
   if (c == LUA_SIGNATURE[0]) {  /* binary file? */
     lf.n = 0;  /* remove possible newline */
     if (filename) {  /* "real" file? */
+      errno = 0;
       lf.f = freopen(filename, "rb", lf.f);  /* reopen in binary mode */
       if (lf.f == NULL) return errfile(L, "reopen", fnameindex);
       skipcomment(lf.f, &c);  /* re-read initial portion */
@@ -823,6 +830,7 @@ LUALIB_API int luaL_loadfilex (lua_State *L, const char *filename,
     lf.buff[lf.n++] = c;  /* 'c' is the first character of the stream */
   status = lua_load(L, getF, &lf, lua_tostring(L, -1), mode);
   readstatus = ferror(lf.f);
+  errno = 0;  /* no useful error number until here */
   if (filename) fclose(lf.f);  /* close file (even in case of errors) */
   if (readstatus) {
     lua_settop(L, fnameindex);  /* ignore results from 'lua_load' */
diff --git a/liolib.c b/liolib.c
index 6879a603..c5075f3e 100644
--- a/liolib.c
+++ b/liolib.c
@@ -245,8 +245,8 @@ static int f_gc (lua_State *L) {
 */
 static int io_fclose (lua_State *L) {
   LStream *p = tolstream(L);
-  int res = fclose(p->f);
-  return luaL_fileresult(L, (res == 0), NULL);
+  errno = 0;
+  return luaL_fileresult(L, (fclose(p->f) == 0), NULL);
 }
 
 
@@ -272,6 +272,7 @@ static int io_open (lua_State *L) {
   LStream *p = newfile(L);
   const char *md = mode;  /* to traverse/check mode */
   luaL_argcheck(L, l_checkmode(md), 2, "invalid mode");
+  errno = 0;
   p->f = fopen(filename, mode);
   return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
 }
@@ -292,6 +293,7 @@ static int io_popen (lua_State *L) {
   const char *mode = luaL_optstring(L, 2, "r");
   LStream *p = newprefile(L);
   luaL_argcheck(L, l_checkmodep(mode), 2, "invalid mode");
+  errno = 0;
   p->f = l_popen(L, filename, mode);
   p->closef = &io_pclose;
   return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
@@ -300,6 +302,7 @@ static int io_popen (lua_State *L) {
 
 static int io_tmpfile (lua_State *L) {
   LStream *p = newfile(L);
+  errno = 0;
   p->f = tmpfile();
   return (p->f == NULL) ? luaL_fileresult(L, 0, NULL) : 1;
 }
@@ -567,6 +570,7 @@ static int g_read (lua_State *L, FILE *f, int first) {
   int nargs = lua_gettop(L) - 1;
   int n, success;
   clearerr(f);
+  errno = 0;
   if (nargs == 0) {  /* no arguments? */
     success = read_line(L, f, 1);
     n = first + 1;  /* to return 1 result */
@@ -660,6 +664,7 @@ static int io_readline (lua_State *L) {
 static int g_write (lua_State *L, FILE *f, int arg) {
   int nargs = lua_gettop(L) - arg;
   int status = 1;
+  errno = 0;
   for (; nargs--; arg++) {
     if (lua_type(L, arg) == LUA_TNUMBER) {
       /* optimization: could be done exactly as for strings */
@@ -678,7 +683,8 @@ static int g_write (lua_State *L, FILE *f, int arg) {
   }
   if (l_likely(status))
     return 1;  /* file handle already on stack top */
-  else return luaL_fileresult(L, status, NULL);
+  else
+    return luaL_fileresult(L, status, NULL);
 }
 
 
@@ -703,6 +709,7 @@ static int f_seek (lua_State *L) {
   l_seeknum offset = (l_seeknum)p3;
   luaL_argcheck(L, (lua_Integer)offset == p3, 3,
                   "not an integer in proper range");
+  errno = 0;
   op = l_fseek(f, offset, mode[op]);
   if (l_unlikely(op))
     return luaL_fileresult(L, 0, NULL);  /* error */
@@ -719,19 +726,25 @@ static int f_setvbuf (lua_State *L) {
   FILE *f = tofile(L);
   int op = luaL_checkoption(L, 2, NULL, modenames);
   lua_Integer sz = luaL_optinteger(L, 3, LUAL_BUFFERSIZE);
-  int res = setvbuf(f, NULL, mode[op], (size_t)sz);
+  int res;
+  errno = 0;
+  res = setvbuf(f, NULL, mode[op], (size_t)sz);
   return luaL_fileresult(L, res == 0, NULL);
 }
 
 
 
 static int io_flush (lua_State *L) {
-  return luaL_fileresult(L, fflush(getiofile(L, IO_OUTPUT)) == 0, NULL);
+  FILE *f = getiofile(L, IO_OUTPUT);
+  errno = 0;
+  return luaL_fileresult(L, fflush(f) == 0, NULL);
 }
 
 
 static int f_flush (lua_State *L) {
-  return luaL_fileresult(L, fflush(tofile(L)) == 0, NULL);
+  FILE *f = tofile(L);
+  errno = 0;
+  return luaL_fileresult(L, fflush(f) == 0, NULL);
 }
 
 
diff --git a/loslib.c b/loslib.c
index ad5a9276..ba80d72c 100644
--- a/loslib.c
+++ b/loslib.c
@@ -155,6 +155,7 @@ static int os_execute (lua_State *L) {
 
 static int os_remove (lua_State *L) {
   const char *filename = luaL_checkstring(L, 1);
+  errno = 0;
   return luaL_fileresult(L, remove(filename) == 0, filename);
 }
 
@@ -162,6 +163,7 @@ static int os_remove (lua_State *L) {
 static int os_rename (lua_State *L) {
   const char *fromname = luaL_checkstring(L, 1);
   const char *toname = luaL_checkstring(L, 2);
+  errno = 0;
   return luaL_fileresult(L, rename(fromname, toname) == 0, NULL);
 }