tcmalloc: large alloc 9223372036854775808 bytes == (nil) @
2014-08-02T22:19:29.549+0000 SEVERE: out of memory, printing stack and exiting:
0xf96c46 0xf964c0 0x1391254 0xf87bbd 0xf7e574 0xf8638d 0xf8b367 0x7b95cc 0x7c99fc 0x7ca072 0x7ca460 0x7b86ff 0x7b9259 0x7f8db75fd7d5 0x7b2069
mongod(_ZN5mongo15printStackTraceERSo+0x26) [0xf96c46]
mongod() [0xf964c0]
mongod(tc_new+0x2c4) [0x1391254]
mongod(ZNSt6vectorIcSaIcEE14_M_fill_insertEN9gnu_cxx17_normal_iteratorIPcS1_EEmRKc+0x8d) [0xf87bbd]
mongod(_ZN5mongo17optionenvironment13OptionsParser14readConfigFileERKSsPSs+0x1e4) [0xf7e574]
mongod(_ZN5mongo17optionenvironment13OptionsParser3runERKNS0_13OptionSectionERKSt6vectorISsSaISsEERKSt3mapISsSsSt4lessISsESaISt4pairIKSsSsEEEPNS0_11EnvironmentE+0x63d) [0xf8638d]
mongod(_ZN5mongo17optionenvironment46_mongoInitializerFunction_StartupOptions_ParseEPNS_18InitializerContextE+0x57) [0xf8b367]
mongod(ZN5boost6detail8function17function_invoker1IPFN5mongo6StatusEPNS3_18InitializerContextEES4_S6_E6invokeERNS1_15function_bufferES6+0xc) [0x7b95cc]
mongod(_ZNK5mongo11Initializer7executeERKSt6vectorISsSaISsEERKSt3mapISsSsSt4lessISsESaISt4pairIKSsSsEEE+0x30c) [0x7c99fc]
mongod(_ZN5mongo21runGlobalInitializersERKSt6vectorISsSaISsEERKSt3mapISsSsSt4lessISsESaISt4pairIKSsSsEEE+0x32) [0x7ca072]
mongod(ZN5mongo21runGlobalInitializersEiPKPKcS3+0x3d0) [0x7ca460]
mongod() [0x7b86ff]
mongod(main+0x9) [0x7b9259]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f8db75fd7d5]
mongod() [0x7b2069]

This should instead say "Can't use a directory as a config file".