vppinfra: add const to char* params of several funcs

These functions do not need modifiable strings.
It helps with linker sections as well as C++ compatibility.
It is a good style to use const where approriate.

Type: refactor
Signed-off-by: void234@gmail.com
Change-Id: I8d1e922197b3594122296e8c1af57e0a8ec0bf3d
diff --git a/src/vppinfra/error.c b/src/vppinfra/error.c
index b2b1a83..374b8b5 100644
--- a/src/vppinfra/error.c
+++ b/src/vppinfra/error.c
@@ -109,8 +109,8 @@
 }
 
 __clib_export void
-_clib_error (int how_to_die,
-	     char *function_name, uword line_number, char *fmt, ...)
+_clib_error (int how_to_die, const char *function_name, uword line_number,
+	     const char *fmt, ...)
 {
   u8 *msg = 0;
   va_list va;
@@ -146,8 +146,8 @@
 }
 
 __clib_export clib_error_t *
-_clib_error_return (clib_error_t * errors,
-		    any code, uword flags, char *where, char *fmt, ...)
+_clib_error_return (clib_error_t *errors, any code, uword flags,
+		    const char *where, const char *fmt, ...)
 {
   clib_error_t *e;
   va_list va;
diff --git a/src/vppinfra/error.h b/src/vppinfra/error.h
index e0e2d47..9eae8ea 100644
--- a/src/vppinfra/error.h
+++ b/src/vppinfra/error.h
@@ -85,10 +85,9 @@
 
 #define clib_error_free(e) e = clib_error_free_vector(e)
 
-extern clib_error_t *_clib_error_return (clib_error_t * errors,
-					 any code,
-					 uword flags,
-					 char *where, char *fmt, ...);
+extern clib_error_t *_clib_error_return (clib_error_t *errors, any code,
+					 uword flags, const char *where,
+					 const char *fmt, ...);
 
 #define clib_error_return_code(e,code,flags,args...) \
   _clib_error_return((e),(code),(flags),(char *)clib_error_function,args)
diff --git a/src/vppinfra/error_bootstrap.h b/src/vppinfra/error_bootstrap.h
index 185f4c6..ae23d1b 100644
--- a/src/vppinfra/error_bootstrap.h
+++ b/src/vppinfra/error_bootstrap.h
@@ -62,9 +62,8 @@
 /* Low level error reporting function.
    Code specifies whether to call exit, abort or nothing at
    all (for non-fatal warnings). */
-extern void _clib_error (int code,
-			 char *function_name,
-			 uword line_number, char *format, ...);
+extern void _clib_error (int code, const char *function_name,
+			 uword line_number, const char *format, ...);
 
 #define ASSERT(truth)					\
 do {							\