build: enforce files.h usage

* cfg.mk (sc_prohibit_close): New syntax-check rule.
* src/util/pci.c (pciWaitForDeviceCleanup): Fix violation.
* .x-sc_prohibit_close: New exceptions.
* Makefile.am (EXTRA_DIST): Distribute new file.

.x-sc_prohibit_close

+^docs/.*
+^HACKING$
+^src/util/files.c$

Makefile.am

@@ -26,6 +26,7 @@ EXTRA_DIST = \
   .x-sc_bindtextdomain \
   .x-sc_m4_quote_check \
   .x-sc_prohibit_asprintf \
+  .x-sc_prohibit_close \
   .x-sc_prohibit_empty_lines_at_EOF \
   .x-sc_prohibit_gethostby \
   .x-sc_prohibit_gethostname \

cfg.mk

@@ -231,6 +231,15 @@ sc_avoid_write:
 	halt='consider using safewrite instead of write'		\
 	  $(_sc_search_regexp)
 
+# Avoid functions that can lead to double-close bugs.
+sc_prohibit_close:
+	@prohibit='\<[f]close *\('					\
+	halt='use VIR_{FORCE_}[F]CLOSE instead of [f]close'		\
+	  $(_sc_search_regexp)
+	@prohibit='\<fdopen *\('					\
+	halt='use VIR_FDOPEN instead of fdopen'				\
+	  $(_sc_search_regexp)
+
 # Similar to the gnulib maint.mk rule for sc_prohibit_strcmp
 # Use STREQLEN or STRPREFIX rather than comparing strncmp == 0, or != 0.
 sc_prohibit_strncmp:

src/util/pci.c

@@ -1095,7 +1095,7 @@ pciWaitForDeviceCleanup(pciDevice *dev, const char *matcher)
         }
     }
 
-    fclose(fp);
+    VIR_FORCE_FCLOSE(fp);
 
     return ret;
 }