Implement pre-error-display hook.

* paxlib/error.c (error_hook): New global.
* paxlib/paxlib.h (error_hook): New extern.
(WARN, ERROR, FATAL_ERROR)
(USAGE_ERROR): Call error_hook (if defined) before error().

2 files changed, 26 insertions, 4 deletions

diff --git a/paxlib/error.c b/paxlib/error.c
index 56903a3..134cef3 100644
--- a/paxlib/error.c
+++ b/paxlib/error.c
@@ -21,6 +21,8 @@
 #include <quote.h>
 #include <quotearg.h>
 
+void (*error_hook) (void);
+
 /* Decode MODE from its binary form in a stat structure, and encode it
    into a 9-byte string STRING, terminated with a NUL.  */
 
diff --git a/paxlib/paxlib.h b/paxlib/paxlib.h
index d0ba45b..d4251d1 100644
--- a/paxlib/paxlib.h
+++ b/paxlib/paxlib.h
@@ -32,6 +32,8 @@
 #define PAXEXIT_DIFFERS 1
 #define PAXEXIT_FAILURE 2
 
+extern void (*error_hook) (void);
+
 /* Both WARN and ERROR write a message on stderr and continue processing,
    however ERROR manages so tar will exit unsuccessfully.  FATAL_ERROR
    writes a message on stderr and aborts immediately, with another message
@@ -41,13 +43,31 @@
    is zero when the error is not being detected by the system.  */
 
 #define WARN(Args) \
-  error Args
+  do { if (error_hook) error_hook (); error Args; } while (0)
 #define ERROR(Args) \
-  (error Args, exit_status = PAXEXIT_FAILURE)
+  do						\
+    {						\
+      if (error_hook) error_hook ();		\
+      error Args;				\
+      exit_status = PAXEXIT_FAILURE;		\
+    }						\
+  while (0)
 #define FATAL_ERROR(Args) \
-  (error Args, fatal_exit ())
+  do						\
+    {						\
+      if (error_hook) error_hook ();		\
+      error Args;				\
+      fatal_exit ();				\
+    }						\
+  while (0)
 #define USAGE_ERROR(Args) \
-  (error Args, usage (PAXEXIT_FAILURE))
+  do						\
+    {						\
+      if (error_hook) error_hook ();		\
+      error Args;				\
+      usage (PAXEXIT_FAILURE);			\
+    }						\
+  while (0)
 
 extern int exit_status;