error: redefinition of ap_hack_apr_allocator_create

Apache Web Server source code compilation is always fun. It’s very rare that Apache will be compiled on the first run on a brand new server.

The fact is it requires a lot of pre-requisite and if any of them is missing or version compatibility then you may have to spend a lot of time on fixing those. I was working on the brand new server with Linux 6.4 to install Apache 2.4.6 and encountered following error.

exports.c:1929:
error: redefinition of 'ap_hack_apr_allocator_create'
exports.c:921: note: previous definition of 'ap_hack_apr_allocator_create' was here exports.c:1930:
error: redefinition of 'ap_hack_apr_allocator_destroy'
exports.c:922: note: previous definition of 'ap_hack_apr_allocator_destroy' was here exports.c:1931:
error: redefinition of 'ap_hack_apr_allocator_alloc' exports.c:923: note: previous definition of 'ap_hack_apr_allocator_alloc' was here exports.c:1932:
error: redefinition of 'ap_hack_apr_allocator_free' exports.c:924: note: previous definition of 'ap_hack_apr_allocator_free' was here exports.c:1933:
error: redefinition of 'ap_hack_apr_allocator_owner_set'
exports.c:925: note: previous definition of 'ap_hack_apr_allocator_owner_set' was here exports.c:1934:
error: redefinition of 'ap_hack_apr_allocator_owner_get' exports.c:926: note: previous definition of 'ap_hack_apr_allocator_owner_get' was here exports.c:1935:
error: redefinition of 'ap_hack_apr_allocator_max_free_set' exports.c:927: note: previous definition of 'ap_hack_apr_allocator_max_free_set' was here exports.c:1937:
error: redefinition of 'ap_hack_apr_allocator_mutex_set' exports.c:929: note: previous definition of 'ap_hack_apr_allocator_mutex_set' was here exports.c:1938:
error: redefinition of 'ap_hack_apr_allocator_mutex_get' exports.c:930: note: previous definition of 'ap_hack_apr_allocator_mutex_get' was here exports.c:1944:
error: redefinition of 'ap_hack_apr_atomic_init' exports.c:936: note: previous definition of 'ap_hack_apr_atomic_init' was here exports.c:1945:
error: redefinition of 'ap_hack_apr_atomic_read32' exports.c:937: note: previous definition of 'ap_hack_apr_atomic_read32' was here exports.c:1946:
error: redefinition of 'ap_hack_apr_atomic_set32' exports.c:938: note: previous definition of 'ap_hack_apr_atomic_set32' was here exports.c:1947:
error: redefinition of 'ap_hack_apr_atomic_add32' exports.c:939: note: previous definition of 'ap_hack_apr_atomic_add32' was here exports.c:1948:
error: redefinition of 'ap_hack_apr_atomic_sub32' exports.c:940: note: previous definition of 'ap_hack_apr_atomic_sub32' was here exports.c:1949:
error: redefinition of 'ap_hack_apr_atomic_inc32' exports.c:941: note: previous definition of 'ap_hack_apr_atomic_inc32' was here exports.c:1950:
error: redefinition of 'ap_hack_apr_atomic_dec32' exports.c:942: note: previous definition of 'ap_hack_apr_atomic_dec32' was here exports.c:1951:
error: redefinition of 'ap_hack_apr_atomic_cas32' exports.c:943: note: previous definition of 'ap_hack_apr_atomic_cas32' was here exports.c:1952:
error: redefinition of 'ap_hack_apr_atomic_xchg32' exports.c:944: note: previous definition of 'ap_hack_apr_atomic_xchg32' was here exports.c:1953:
error: redefinition of 'ap_hack_apr_atomic_casptr' exports.c:945: note: previous definition of 'ap_hack_apr_atomic_casptr' was here exports.c:1954:
error: redefinition of 'ap_hack_apr_atomic_xchgptr' exports.c:946: note: previous definition of 'ap_hack_apr_atomic_xchgptr' was here exports.c:1960:
error: redefinition of 'ap_hack_apr_dso_load' exports.c:1085: note: previous definition of 'ap_hack_apr_dso_load' was here exports.c:1961:
error: redefinition of 'ap_hack_apr_dso_unload' exports.c:1086: note: previous definition of 'ap_hack_apr_dso_unload' was here exports.c:1962:
error: redefinition of 'ap_hack_apr_dso_sym' exports.c:1087: note: previous definition of 'ap_hack_apr_dso_sym' was here exports.c:1963:
error: redefinition of 'ap_hack_apr_dso_error' exports.c:1088: note: previous definition of 'ap_hack_apr_dso_error' was here exports.c:1969:
error: redefinition of 'ap_hack_apr_env_get' exports.c:1094: note: previous definition of 'ap_hack_apr_env_get' was here exports.c:1970:
error: redefinition of 'ap_hack_apr_env_set' exports.c:1095: note: previous definition of 'ap_hack_apr_env_set' was here exports.c:1971:
error: redefinition of 'ap_hack_apr_env_delete' exports.c:1096: note: previous definition of 'ap_hack_apr_env_delete' was here exports.c:1976:
error: redefinition of 'ap_hack_apr_strerror' exports.c:1101: note: previous definition of 'ap_hack_apr_strerror' was here export.c:1981:
error: redefinition of 'ap_hack_apr_stat' exports.c:1106: note: previous definition of 'ap_hack_apr_stat' was here exports.c:1982:
error: redefinition of 'ap_hack_apr_dir_open' exports.c:1107: note: previous definition of 'ap_hack_apr_dir_open' was here exports.c:1983:
error: redefinition of 'ap_hack_apr_dir_close' exports.c:1108: note: previous definition of 'ap_hack_apr_dir_close' was here 

If you are getting a similar error, you can fix it as I did by following.

Solution:

After looking into various parameters, I noticed this happens when you have apr-util lower version than 1.4.1

• Verify your apr-util version. If you find lower version then you must install the 1.4.1 or higher
• Download apr-util source code from http://mirror.nus.edu.sg/apache/apr/
• Extract the downloaded file

Compile and install as following

./configure make make install

Default, it will install under /usr/local/apr/bin/apu-1-config. Now you can compline apache with newly installed apr-util and you should be good.

./configure --with-apr-util=/usr/local/apr/bin/apu-1-config

Does it help?