mmap_read/mmap_shared on zero length files no longer fail but return a

zero length buffer

CHANGES

@@ -24,6 +24,8 @@
   add io_fd_flags so the caller can tell io_fd whether the socket is blocking
     (saves one fcntl syscall)
   more constness for stralloc and buffer
+  mmap_read/mmap_shared on zero length files no longer fail but return a
+    zero length buffer
 
 0.29:
   save 8 bytes in taia.h for 64-bit systems

mmap/mmap_read.c

@@ -30,9 +30,12 @@ extern const char* mmap_read(const char* filename,size_t * filesize) {
     register off_t o=lseek(fd,0,SEEK_END);
     if (sizeof(off_t)!=sizeof(size_t) && o > (off_t)(size_t)-1) { close(fd); return 0; }
     *filesize=(size_t)o;
+    if (o>0) {
       map=mmap(0,*filesize,PROT_READ,MAP_SHARED,fd,0);
       if (map==(char*)-1)
 	map=0;
+    } else
+      map="";
     close(fd);
     return map;
   }

mmap/mmap_shared.c

@@ -30,9 +30,12 @@ extern char* mmap_shared(const char* filename,size_t * filesize) {
     register off_t o=lseek(fd,0,SEEK_END);
     if (sizeof(off_t)!=sizeof(size_t) && o > (off_t)(size_t)-1) { close(fd); return 0; }
     *filesize=(size_t)o;
+    if (o) {
       map=mmap(0,*filesize,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
       if (map==(char*)-1)
 	map=0;
+    } else
+      map="";
     close(fd);
     return map;
   }

mmap/mmap_unmap.c

@@ -13,6 +13,6 @@ int mmap_unmap(const char* mapped,size_t maplen) {
   (void)maplen;
   return UnmapViewOfFile(mapped)?0:-1;
 #else
-  return munmap((char*)mapped,maplen);
+  return maplen ? munmap((char*)mapped,maplen) : 0;
 #endif
 }