preprocessing gcc vs clang - majianpeng/majianpeng.github.io GitHub Wiki

preprocessing stage

compare

clang

typedef uint8_t WriteLogCacheEntry_toid_type_num[((2 + 1 - (sizeof(_pobj_layout_rbd_pwl_ref)))) + 1];union WriteLogCacheEntry_toid{ WriteLogCacheEntry_toid(){ } WriteLogCacheEntry_toid(PMEMoid _oid) : oid(_oid){ } PMEMoid oid; struct WriteLogCacheEntry *_type; WriteLogCacheEntry_toid_type_num *_type_num;};;

gcc

# 205 "librbd/cache/pwl/Types.h" WriteLogCacheEntry_toid_type_num # 205 "librbd/cache/pwl/Types.h" 3 4 [((2 + 1 - (sizeof(_pobj_layout_rbd_pwl_ref)))) + 1];union # 205 "librbd/cache/pwl/Types.h" WriteLogCacheEntry_toid # 205 "librbd/cache/pwl/Types.h" 3 4 { # 205 "librbd/cache/pwl/Types.h" WriteLogCacheEntry_toid # 205 "librbd/cache/pwl/Types.h" 3 4 (){ } # 205 "librbd/cache/pwl/Types.h" WriteLogCacheEntry_toid # 205 "librbd/cache/pwl/Types.h" 3 4 (PMEMoid _oid) : oid(_oid){ } PMEMoid oid; # 205 "librbd/cache/pwl/Types.h" struct WriteLogCacheEntry # 205 "librbd/cache/pwl/Types.h" 3 4 *_type; # 205 "librbd/cache/pwl/Types.h" WriteLogCacheEntry_toid_type_num # 205 "librbd/cache/pwl/Types.h" 3 4 *_type_num;}; # 205 "librbd/cache/pwl/Types.h"

• But we can use "c++ -E -P" to get the same result of clang++.

Summary:

format of output of Clang is better and make more readable.