[master] enable ISC_BUFFER_USEINLINE to be overridden

OPTIONS

@@ -22,4 +22,7 @@ Setting                   Description
                           Increase the maximum number of configurable
 -DNS_RPZ_MAX_ZONES=64     response policy zones from 32 to 64; this is the
                           highest possible setting
+                          Disable the use of inline functions to implement
+-DISC_BUFFER_USEINLINE=0  the isc_buffer API: this reduces performance but
+                          may be useful when debugging
 

OPTIONS.md

@@ -21,3 +21,4 @@ Some of these settings are:
 |`-DCHECK_LOCAL=0`|Don't check out-of-zone addresses in `named-checkzone`|
 |`-DNS_RUN_PID_DIR=0`|Create default PID files in `${localstatedir}/run` rather than `${localstatedir}/run/named/`|
 |`-DNS_RPZ_MAX_ZONES=64`|Increase the maximum number of configurable response policy zones from 32 to 64; this is the highest possible setting|
+|`-DISC_BUFFER_USEINLINE=0`|Disable the use of inline functions to implement the `isc_buffer` API: this reduces performance but may be useful when debugging |

lib/isc/include/isc/buffer.h

@@ -104,10 +104,12 @@
 #include <isc/types.h>
 
 /*!
- * To make many functions be inline macros (via \#define) define this.
- * If it is undefined, a function will be used.
+ * To make many functions be inline macros (via \#define) define this to 1.
+ * To use continue to use them as functions define this to 0.
  */
+#ifndef ISC_BUFFER_USEINLINE
 #define ISC_BUFFER_USEINLINE 1
+#endif
 
 ISC_LANG_BEGINDECLS
 
@@ -1007,7 +1009,7 @@ ISC_LANG_ENDDECLS
 		_cp[3] = (unsigned char)_val2; \
 	} while (0)
 
-#if defined(ISC_BUFFER_USEINLINE)
+#if ISC_BUFFER_USEINLINE
 #define isc_buffer_init			ISC__BUFFER_INIT
 #define isc_buffer_initnull		ISC__BUFFER_INITNULL
 #define isc_buffer_invalidate		ISC__BUFFER_INVALIDATE