I discovered a couple months ago that GDB could not generate backtraces on my system, and this was confirmed recently when I was having KDevelop trouble and was again unable to get a backtrace even when compiling it with the appropriate options. The bug in question is http://bugs.gentoo.org/show_bug.cgi?id=103656#c6. The following small program displays this behavior on my system: int main() { int *ptr = (int *) 0x12345678; *ptr = 10; return 0; } It just accesses some odd address, nothing fancy. The output from GDB, after compilation with "gcc -g -o crash crash.c", is as follows: tommstein@Morpheus ~ $ gdb ./crash GNU gdb 6.3 Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-pc-linux-gnu"...Using host libthread_db library "/lib/tls/libthread_db.so.1". (gdb) run Starting program: /home/tommstein/crash Program received signal SIGSEGV, Segmentation fault. 0x0000555555554a2a in ?? () (gdb) bt #0 0x0000555555554a2a in ?? () #1 0x0000555555554ac0 in ?? () #2 0x0000000012345678 in ?? () #3 0x5489ed33ce913305 in ?? () #4 0x0000000000000000 in ?? () #5 0x00002aaaaabc0c20 in ?? () #6 0x00002aaaaabde6a4 in ?? () #7 0x0000000000000000 in ?? () #8 0x00007fffffffe028 in ?? () #9 0x00000001aade1ec0 in ?? () #10 0x0000555555554a08 in ?? () #11 0x0000000000000000 in ?? () #12 0x00002aaaaabc0c20 in ?? () #13 0x0000555555554a60 in ?? () #14 0x00007fffffffe020 in ?? () #15 0x0000000000000000 in ?? () #16 0x0000000000000000 in ?? () #17 0x00007fffffffdf60 in ?? () #18 0x00002aaaaabde65f in ?? () #19 0x00007fff00000000 in ?? () #20 0x0000000000000000 in ?? () #21 0x0000000000000000 in ?? () #22 0x00002aaaaaab594b in ?? () #23 0x0000000000000000 in ?? () #24 0x0000000000000000 in ?? () #25 0x0000000000000000 in ?? () #26 0x0000000000000000 in ?? () #27 0x0000555555554940 in ?? () #28 0x000055555555496a in ?? () #29 0x00007fffffffe018 in ?? () #30 0x000000000000001c in ?? () #31 0x0000000000000001 in ?? () #32 0x00007fffffffe305 in ?? () #33 0x0000000000000000 in ?? () #34 0x00007fffffffe31b in ?? () #35 0x00007fffffffe3c8 in ?? () #36 0x00007fffffffe3dc in ?? () #37 0x00007fffffffe3f7 in ?? () #38 0x00007fffffffe409 in ?? () #39 0x00007fffffffe419 in ?? () #40 0x00007fffffffe424 in ?? () #41 0x00007fffffffe470 in ?? () #42 0x00007fffffffe4d7 in ?? () #43 0x00007fffffffe4f5 in ?? () #44 0x00007fffffffe553 in ?? () #45 0x00007fffffffe565 in ?? () #46 0x00007fffffffe575 in ?? () #47 0x00007fffffffe58b in ?? () #48 0x00007fffffffe59d in ?? () #49 0x00007fffffffe5ac in ?? () #50 0x00007fffffffe5d5 in ?? () #51 0x00007fffffffe9f0 in ?? () #52 0x00007fffffffe9fe in ?? () #53 0x00007fffffffea23 in ?? () #54 0x00007fffffffea54 in ?? () #55 0x00007fffffffea87 in ?? () #56 0x00007fffffffea93 in ?? () #57 0x00007fffffffeac0 in ?? () #58 0x00007fffffffead4 in ?? () #59 0x00007fffffffeaf9 in ?? () #60 0x00007fffffffeb18 in ?? () #61 0x00007fffffffeb44 in ?? () #62 0x00007fffffffebfd in ?? () #63 0x00007fffffffec15 in ?? () #64 0x00007fffffffec21 in ?? () #65 0x00007fffffffec35 in ?? () #66 0x00007fffffffec6b in ?? () #67 0x00007fffffffec7c in ?? () #68 0x00007fffffffec8c in ?? () #69 0x00007fffffffec99 in ?? () #70 0x00007fffffffecad in ?? () #71 0x00007fffffffecb6 in ?? () #72 0x00007fffffffecc3 in ?? () #73 0x00007fffffffecd8 in ?? () #74 0x00007fffffffece0 in ?? () #75 0x00007fffffffecf6 in ?? () #76 0x00007fffffffed08 in ?? () #77 0x00007fffffffed28 in ?? () #78 0x00007fffffffed30 in ?? () #79 0x00007fffffffed3b in ?? () #80 0x00007fffffffed47 in ?? () #81 0x00007fffffffed73 in ?? () #82 0x00007fffffffed8c in ?? () #83 0x00007fffffffee2f in ?? () ---Type <return> to continue, or q <return> to quit--- #84 0x00007fffffffee3c in ?? () #85 0x00007fffffffee52 in ?? () #86 0x00007fffffffee6e in ?? () #87 0x00007fffffffefc2 in ?? () #88 0x00007fffffffefd7 in ?? () #89 0x0000000000000000 in ?? () #90 0x0000000000000010 in ?? () #91 0x00000000078bfbff in ?? () #92 0x0000000000000006 in ?? () #93 0x0000000000001000 in ?? () #94 0x0000000000000011 in ?? () #95 0x0000000000000064 in ?? () #96 0x0000000000000003 in ?? () #97 0x0000555555554040 in ?? () #98 0x0000000000000004 in ?? () #99 0x0000000000000038 in ?? () #100 0x0000000000000005 in ?? () #101 0x000000000000000a in ?? () #102 0x0000000000000007 in ?? () #103 0x00002aaaaaaab000 in ?? () #104 0x0000000000000008 in ?? () #105 0x0000000000000000 in ?? () #106 0x0000000000000009 in ?? () #107 0x0000555555554940 in ?? () #108 0x000000000000000b in ?? () #109 0x00000000000003e8 in ?? () #110 0x000000000000000c in ?? () #111 0x00000000000003e8 in ?? () #112 0x000000000000000d in ?? () #113 0x0000000000000064 in ?? () #114 0x000000000000000e in ?? () #115 0x0000000000000064 in ?? () #116 0x0000000000000017 in ?? () #117 0x0000000000000000 in ?? () #118 0x000000000000000f in ?? () #119 0x00007fffffffe2fe in ?? () #120 0x0000000000000000 in ?? () #121 0x0000000000000000 in ?? () #122 0x3878000000000000 in ?? () #123 0x6f682f0034365f36 in ?? () #124 0x736d6d6f742f656d in ?? () #125 0x6172632f6e696574 in ?? () #126 0x41504e414d006873 in ?? () #127 0x2f7273752f3d4854 in ?? () #128 0x68732f6c61636f6c in ?? () #129 0x3a6e616d2f657261 in ?? () #130 0x6168732f7273752f in ?? () #131 0x2f3a6e616d2f6572 in ?? () #132 0x726168732f727375 in ?? () #133 0x6974756e69622f65 in ?? () #134 0x2f617461642d736c in ?? () #135 0x702d34365f363878 in ?? () #136 0x2d78756e696c2d63 in ?? () #137 0x35312e322f756e67 in ?? () #138 0x2f322e302e32392e in ?? () #139 0x7273752f3a6e616d in ?? () #140 0x672f65726168732f in ?? () #141 0x2f617461642d6363 in ?? () #142 0x702d34365f363878 in ?? () #143 0x2d78756e696c2d63 in ?? () #144 0x2e342e332f756e67 in ?? () #145 0x752f3a6e616d2f34 in ?? () #146 0x2f332f74712f7273 in ?? () #147 0x006e616d2f636f64 in ?? () #148 0x544c554d5f45444b in ?? () #149 0x61663d4441454849 in ?? () #150 0x435f4d440065736c in ?? () #151 0x2f3d4c4f52544e4f in ?? () #152 0x2f6e75722f726176 in ?? () #153 0x48006c74636d6478 in ?? () #154 0x3d454d414e54534f in ?? () #155 0x7375656870726f4d in ?? () #156 0x2f3d4c4c45485300 in ?? () #157 0x687361622f6e6962 in ?? () #158 0x74783d4d52455400 in ?? () #159 0x5f4d4458006d7265 in ?? () #160 0x3d444547414e414d in ?? () #161 0x6e75722f7261762f in ?? () #162 0x2f6c74636d64782f in ?? () #163 0x3a2d6c74636d6478 in ?? () #164 0x2c647379616d2c30 in ?? () #165 0x63732c6e6679616d in ?? () #166 0x647673722c646568 in ?? () #167 0x3d646f6874656d2c in ?? () ---Type <return> to continue, or q <return> to quit--- #168 0x0063697373616c63 in ?? () #169 0x5f43525f324b5447 in ?? () #170 0x652f3d53454c4946 in ?? () #171 0x322d6b74672f6374 in ?? () #172 0x63726b74672f302e in ?? () #173 0x742f656d6f682f3a in ?? () #174 0x6e696574736d6d6f in ?? () #175 0x2d63726b74672e2f in ?? () #176 0x6d6f682f3a302e32 in ?? () #177 0x74736d6d6f742f65 in ?? () #178 0x65646b2e2f6e6965 in ?? () #179 0x726168732f342e33 in ?? () #180 0x6769666e6f632f65 in ?? () #181 0x470063726b74672f in ?? () #182 0x682f3d42494c5f53 in ?? () #183 0x6d6d6f742f656d6f in ?? () #184 0x662e2f6e69657473 in ?? () #185 0x4b54470073746e6f in ?? () #186 0x454c49465f43525f in ?? () #187 0x672f6374652f3d53 in ?? () #188 0x63726b74672f6b74 in ?? () #189 0x742f656d6f682f3a in ?? () #190 0x6e696574736d6d6f in ?? () #191 0x3a63726b74672e2f in ?? () #192 0x6f742f656d6f682f in ?? () #193 0x2f6e696574736d6d in ?? () #194 0x2f342e3365646b2e in ?? () #195 0x6f632f6572616873 in ?? () #196 0x6b74672f6769666e in ?? () #197 0x4f444e4957006372 in ?? () #198 0x373930323d444957 in ?? () #199 0x4454510035323531 in ?? () #200 0x2f7273752f3d5249 in ?? () #201 0x45444b00332f7471 in ?? () #202 0x45535f4c4c55465f in ?? () #203 0x72743d4e4f495353 in ?? () #204 0x4c415f434c006575 in ?? () #205 0x2e53555f6e653d4c in ?? () #206 0x4553550038667475 in ?? () #207 0x74736d6d6f743d52 in ?? () #208 0x4c455250006e6965 in ?? () #209 0x485441505f4b4e49 in ?? () #210 0x752f3d4b53414d5f in ?? () #211 0x672f62696c2f7273 in ?? () #212 0x72656d6165727473 in ?? () #213 0x5f534c00382e302d in ?? () #214 0x6e3d53524f4c4f43 in ?? () #215 0x3d69663a30303d6f in ?? () #216 0x31303d69643a3030 in ?? () #217 0x303d6e6c3a34333b in ?? () #218 0x3d69703a36333b31 in ?? () #219 0x6f733a33333b3034 in ?? () #220 0x643a35333b31303d in ?? () #221 0x3a35333b31303d6f in ?? () #222 0x33333b30343d6462 in ?? () #223 0x343d64633a31303b in ?? () #224 0x3a31303b33333b30 in ?? () #225 0x35303b31303d726f in ?? () #226 0x6d3a31343b37333b in ?? () #227 0x3b35303b31303d69 in ?? () #228 0x78653a31343b3733 in ?? () #229 0x2a3a32333b31303d in ?? () #230 0x3b31303d646d632e in ?? () #231 0x6578652e2a3a3233 in ?? () #232 0x2a3a32333b31303d in ?? () #233 0x3b31303d6d6f632e in ?? () #234 0x6d74622e2a3a3233 in ?? () #235 0x2a3a32333b31303d in ?? () #236 0x3b31303d7461622e in ?? () #237 0x3d68732e2a3a3233 in ?? () #238 0x2e2a3a32333b3130 in ?? () #239 0x333b31303d687363 in ?? () #240 0x3d7261742e2a3a32 in ?? () #241 0x2e2a3a31333b3130 in ?? () #242 0x333b31303d7a6774 in ?? () #243 0x3d6a72612e2a3a31 in ?? () #244 0x2e2a3a31333b3130 in ?? () #245 0x333b31303d7a6174 in ?? () #246 0x3d687a6c2e2a3a31 in ?? () #247 0x2e2a3a31333b3130 in ?? () #248 0x333b31303d70697a in ?? () #249 0x31303d7a2e2a3a31 in ?? () #250 0x3d5a2e2a3a31333b in ?? () #251 0x2e2a3a31333b3130 in ?? () ---Type <return> to continue, or q <return> to quit--- #252 0x31333b31303d7a67 in ?? () #253 0x303d327a622e2a3a in ?? () #254 0x622e2a3a31333b31 in ?? () #255 0x3a31333b31303d7a in ?? () #256 0x303d327a62742e2a in ?? () #257 0x742e2a3a31333b31 in ?? () #258 0x3a31333b31303d7a in ?? () #259 0x31303d6265642e2a in ?? () #260 0x70722e2a3a31333b in ?? () #261 0x3a31333b31303d6d in ?? () #262 0x31303d7261722e2a in ?? () #263 0x63612e2a3a31333b in ?? () #264 0x3a31333b31303d65 in ?? () #265 0x31303d6f6f7a2e2a in ?? () #266 0x70632e2a3a31333b in ?? () #267 0x31333b31303d6f69 in ?? () #268 0x31303d7a372e2a3a in ?? () #269 0x7a722e2a3a31333b in ?? () #270 0x2a3a31333b31303d in ?? () #271 0x3b31303d67706a2e in ?? () #272 0x65706a2e2a3a3533 in ?? () #273 0x3a35333b31303d67 in ?? () #274 0x31303d6669672e2a in ?? () #275 0x6d622e2a3a35333b in ?? () #276 0x3a35333b31303d70 in ?? () #277 0x31303d6d70702e2a in ?? () #278 0x67742e2a3a35333b in ?? () #279 0x3a35333b31303d61 in ?? () #280 0x31303d6d62782e2a in ?? () #281 0x70782e2a3a35333b in ?? () #282 0x3a35333b31303d6d in ?? () #283 0x31303d6669742e2a in ?? () #284 0x69742e2a3a35333b in ?? () #285 0x35333b31303d6666 in ?? () #286 0x303d676e702e2a3a in ?? () #287 0x6d2e2a3a35333b31 in ?? () #288 0x35333b31303d676e in ?? () #289 0x303d6663782e2a3a in ?? () #290 0x702e2a3a35333b31 in ?? () #291 0x35333b31303d7863 in ?? () #292 0x303d67706d2e2a3a in ?? () #293 0x6d2e2a3a35333b31 in ?? () #294 0x333b31303d676570 in ?? () #295 0x3d76326d2e2a3a35 in ?? () #296 0x2e2a3a35333b3130 in ?? () #297 0x333b31303d697661 in ?? () #298 0x3d766b6d2e2a3a35 in ?? () #299 0x2e2a3a35333b3130 in ?? () #300 0x333b31303d6d676f in ?? () #301 0x3d34706d2e2a3a35 in ?? () #302 0x2e2a3a35333b3130 in ?? () #303 0x333b31303d76346d in ?? () #304 0x7634706d2e2a3a35 in ?? () #305 0x2a3a35333b31303d in ?? () #306 0x3b31303d766f6d2e in ?? () #307 0x3d74712e2a3a3533 in ?? () #308 0x2e2a3a35333b3130 in ?? () #309 0x333b31303d766d77 in ?? () #310 0x3d6673612e2a3a35 in ?? () #311 0x2e2a3a35333b3130 in ?? () #312 0x35333b31303d6d72 in ?? () #313 0x3d62766d722e2a3a in ?? () #314 0x2e2a3a35333b3130 in ?? () #315 0x333b31303d636c66 in ?? () #316 0x3d696c662e2a3a35 in ?? () #317 0x2e2a3a35333b3130 in ?? () #318 0x35333b31303d6c67 in ?? () #319 0x31303d6c642e2a3a in ?? () #320 0x64702e2a3a35333b in ?? () #321 0x3a32333b30303d66 in ?? () #322 0x3b30303d73702e2a in ?? () #323 0x7478742e2a3a3233 in ?? () #324 0x2a3a32333b30303d in ?? () #325 0x303d68637461702e in ?? () #326 0x642e2a3a32333b30 in ?? () #327 0x333b30303d666669 in ?? () #328 0x3d676f6c2e2a3a32 in ?? () #329 0x2e2a3a32333b3030 in ?? () #330 0x333b30303d786574 in ?? () #331 0x3d636f642e2a3a32 in ?? () #332 0x2e2a3a32333b3030 in ?? () #333 0x333b30303d33706d in ?? () #334 0x3d7661772e2a3a36 in ?? () #335 0x2e2a3a36333b3030 in ?? () ---Type <return> to continue, or q <return> to quit--- #336 0x333b30303d64696d in ?? () #337 0x6964696d2e2a3a36 in ?? () #338 0x2a3a36333b30303d in ?? () #339 0x333b30303d75612e in ?? () #340 0x3d67676f2e2a3a36 in ?? () #341 0x2e2a3a36333b3030 in ?? () #342 0x3b30303d63616c66 in ?? () #343 0x6361612e2a3a3633 in ?? () #344 0x003a36333b30303d in ?? () #345 0x5f4553555f4b4447 in ?? () #346 0x554700313d544658 in ?? () #347 0x44414f4c5f454c49 in ?? () #348 0x752f3d485441505f in ?? () #349 0x65726168732f7273 in ?? () #350 0x312f656c6975672f in ?? () #351 0x4f4854595000362e in ?? () #352 0x752f3d53434f444e in ?? () #353 0x65726168732f7273 in ?? () #354 0x7479702f636f642f in ?? () #355 0x73636f642d6e6f68 in ?? () #356 0x682f352e332e322d in ?? () #357 0x53534553006c6d74 in ?? () #358 0x414e414d5f4e4f49 in ?? () #359 0x61636f6c3d524547 in ?? () #360 0x656870726f4d2f6c in ?? () #361 0x2f706d742f3a7375 in ?? () #362 0x696e752d4543492e in ?? () #363 0x4300303531382f78 in ?? () #364 0x323d534e4d554c4f in ?? () #365 0x49464e4f43003235 in ?? () #366 0x4345544f52505f47 in ?? () #367 0x2f3d4b53414d5f54 in ?? () #368 0x6e6f63672f637465 in ?? () #369 0x742f6374652f2066 in ?? () #370 0x006f666e696d7265 in ?? () #371 0x752f3d5245474150 in ?? () #372 0x6c2f6e69622f7273 in ?? () #373 0x5f47445800737365 in ?? () #374 0x445f4749464e4f43 in ?? () #375 0x7273752f3d535249 in ?? () #376 0x342e332f65646b2f in ?? () #377 0x6764782f6374652f in ?? () #378 0x435254494e495800 in ?? () #379 0x31582f6374652f3d in ?? () #380 0x2f74696e69782f31 in ?? () #381 0x00637274696e6978 in ?? () #382 0x5f454c4f534e4f4b in ?? () #383 0x4f43443d504f4344 in ?? () #384 0x6e6f6b2866655250 in ?? () #385 0x3832312d656c6f73 in ?? () #386 0x6f736e6f6b2c3737 in ?? () #387 0x485441500029656c in ?? () #388 0x646b2f7273752f3d in ?? () #389 0x69622f342e332f65 in ?? () #390 0x6c2f7273752f3a6e in ?? () #391 0x6e69622f6c61636f in ?? () #392 0x69622f7273752f3a in ?? () #393 0x2f3a6e69622f3a6e in ?? () #394 0x3a6e69622f74706f in ?? () #395 0x3638782f7273752f in ?? () #396 0x6c2d63702d34365f in ?? () #397 0x756e672d78756e69 in ?? () #398 0x6e69622d6363672f in ?? () #399 0x2f3a342e342e332f in ?? () #400 0x332f74712f727375 in ?? () #401 0x73752f3a6e69622f in ?? () #402 0x2e332f65646b2f72 in ?? () #403 0x752f3a6e69622f34 in ?? () #404 0x332f65646b2f7273 in ?? () #405 0x2f3a6e69622f332e in ?? () #406 0x656d61672f727375 in ?? 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() #435 0x3d454d4f4800313d in ?? () #436 0x6f742f656d6f682f in ?? () #437 0x006e696574736d6d in ?? () #438 0x00323d4c564c4853 in ?? () #439 0x5f524f5352554358 in ?? () #440 0x65643d454d454854 in ?? () #441 0x4f4c00746c756166 in ?? () #442 0x6f743d454d414e47 in ?? () #443 0x006e696574736d6d in ?? () #444 0x41504e4f48545950 in ?? () #445 0x2f7273752f3d4854 in ?? () #446 0x74726f702f62696c in ?? () #447 0x006d79702f656761 in ?? () #448 0x00522d3d5353454c in ?? () #449 0x434550535f434347 in ?? () #450 0x525f535643003d53 in ?? () #451 0x58006873733d4853 in ?? () #452 0x5f415441445f4744 in ?? () #453 0x73752f3d53524944 in ?? () #454 0x2e332f65646b2f72 in ?? () #455 0x3a65726168732f34 in ?? () #456 0x6168732f7273752f in ?? () #457 0x4f5353454c006572 in ?? () #458 0x73656c7c3d4e4550 in ?? () #459 0x68732e6570697073 in ?? () #460 0x4f464e4900732520 in ?? () #461 0x73752f3d48544150 in ?? () #462 0x2f65726168732f72 in ?? () #463 0x73752f3a6f666e69 in ?? () #464 0x2f65726168732f72 in ?? () #465 0x736c6974756e6962 in ?? () #466 0x38782f617461642d in ?? () #467 0x2d63702d34365f36 in ?? () #468 0x6e672d78756e696c in ?? () #469 0x392e35312e322f75 in ?? () #470 0x6e692f322e302e32 in ?? () #471 0x2f7273752f3a6f66 in ?? () #472 0x63672f6572616873 in ?? () #473 0x782f617461642d63 in ?? () #474 0x63702d34365f3638 in ?? () #475 0x672d78756e696c2d in ?? () #476 0x342e342e332f756e in ?? () #477 0x752f3a6f666e692f in ?? () #478 0x65726168732f7273 in ?? () #479 0x6d652f6f666e692f in ?? () #480 0x440031322d736361 in ?? () #481 0x3a3d59414c505349 in ?? () #482 0x4e45504f00302e30 in ?? () #483 0x49464f52505f4c47 in ?? () #484 0x696469766e3d454c in ?? () #485 0x435f454e41530061 in ?? () #486 0x49445f4749464e4f in ?? () #487 0x732f6374652f3d52 in ?? () #488 0x4f4300642e656e61 in ?? () #489 0x4f52505f4749464e in ?? () #490 0x73752f3d54434554 in ?? () #491 0x31582f62696c2f72 in ?? () #492 0x752f20626b782f31 in ?? () #493 0x332f65646b2f7273 in ?? () #494 0x65726168732f342e in ?? () #495 0x206769666e6f632f in ?? () #496 0x65646b2f7273752f in ?? () #497 0x766e652f342e332f in ?? () #498 0x646b2f7273752f20 in ?? () #499 0x68732f342e332f65 in ?? () #500 0x2f206e776f647475 in ?? () #501 0x2f65646b2f727375 in ?? () #502 0x726168732f332e33 in ?? () #503 0x6769666e6f632f65 in ?? () ---Type <return> to continue, or q <return> to quit--- #504 0x646b2f7273752f20 in ?? () #505 0x6e652f332e332f65 in ?? () #506 0x6b2f7273752f2076 in ?? () #507 0x732f332e332f6564 in ?? () #508 0x206e776f64747568 in ?? () #509 0x6168732f7273752f in ?? () #510 0x666d7865742f6572 in ?? () #511 0x6e65672f7865742f in ?? () #512 0x6e6f632f63697265 in ?? () #513 0x73752f202f676966 in ?? () #514 0x2f65726168732f72 in ?? () #515 0x65742f666d786574 in ?? () #516 0x786574616c702f78 in ?? () #517 0x2f6769666e6f632f in ?? () #518 0x68732f7273752f20 in ?? () #519 0x6d7865742f657261 in ?? () #520 0x2f73706976642f66 in ?? () #521 0x202f6769666e6f63 in ?? () #522 0x6168732f7273752f in ?? () #523 0x666d7865742f6572 in ?? () #524 0x6d6664706976642f in ?? () #525 0x2f6769666e6f632f in ?? () #526 0x68732f7273752f20 in ?? () #527 0x6d7865742f657261 in ?? () #528 0x202f697664782f66 in ?? () #529 0x6168732f7273752f in ?? () #530 0x69666e6f632f6572 in ?? () #531 0x4b4f52425f470067 in ?? () #532 0x4e454c49465f4e45 in ?? () #533 0x4300313d53454d41 in ?? () #534 0x4d524554524f4c4f in ?? () #535 0x2f656d6f682f003d in ?? () #536 0x696574736d6d6f74 in ?? () #537 0x0068736172632f6e in ?? () #538 0x0000000000000000 in ?? () Cannot access memory at address 0x7ffffffff000 (gdb) I don't know whether for sure whether the problem is in GDB, GCC, or elsewhere, but I did recently recompile both GDB and GCC, and the problem is obviously still there. Reproducible: Always Steps to Reproduce: 1. Write or obtain a program that crashes 2. Run the above program in GDB (making sure to compile it with -g) 3. Behold how you get a huge, useless backtrace Actual Results: I got the useless backtrace pasted above. Expected Results: Generated a correct backtrace. My processors are dual Opterons, should that information be relevant. Portage 2.0.51.22-r2 (default-linux/amd64/2005.0, gcc-3.4.4, glibc-2.3.5-r1, 2.6.11-gentoo-r11 x86_64) ================================================================= System uname: 2.6.11-gentoo-r11 x86_64 AMD Opteron(tm) Processor 246 Gentoo Base System version 1.6.13 dev-lang/python: 2.3.5 sys-apps/sandbox: 1.2.12 sys-devel/autoconf: 2.13, 2.59-r6 sys-devel/automake: 1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6 sys-devel/binutils: 2.15.92.0.2-r10 sys-devel/libtool: 1.5.18-r1 virtual/os-headers: 2.6.11-r2 ACCEPT_KEYWORDS="amd64" AUTOCLEAN="yes" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=opteron -O3 -pipe" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/kde/2/share/config /usr/kde/3.3/env /usr/kde/3.3/share/config /usr/kde/3.3/shutdown /usr/kde/3.4/env /usr/kde/3.4/share/config /usr/kde/3.4/shutdown /usr/kde/3/share/config /usr/lib/X11/xkb /usr/share/config /usr/share/texmf/dvipdfm/config/ /usr/share/texmf/dvips/config/ /usr/share/texmf/tex/generic/config/ /usr/share/texmf/tex/platex/config/ /usr/share/texmf/xdvi/ /var/qmail/control" CONFIG_PROTECT_MASK="/etc/gconf /etc/terminfo /etc/env.d" CXXFLAGS="-march=opteron -O3 -pipe" DISTDIR="/usr/portage/distfiles" FEATURES="autoconfig distlocks sandbox sfperms strict" GENTOO_MIRRORS="http://distfiles.gentoo.org http://distro.ibiblio.org/pub/Linux/distributions/gentoo" LANG="en_US.utf8" LC_ALL="en_US.utf8" MAKEOPTS="-j3" PKGDIR="/usr/portage/packages" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" SYNC="rsync://rsync.gentoo.org/gentoo-portage" USE="amd64 X Xaw3d a52 aac aalib accessibility acl acpi adns aim alsa apache2 arts audiofile avi bash-completion bcmath berkdb bidi bitmap-fonts bluetooth bmp bonobo bzlib calendar canna cdb cdparanoia cdr chasen cjk crypt cscope ctype cups curl curlwrappers db2 dba dbase dbm dbx dedicated dga dio directfb doc dv dvb dvd dvdr dvdread eds emacs emacs-w3 emul-linux-x86 encode esd ethereal evo examples exif expat fam fastcgi fbcon ffmpeg flac flash flatfile foomaticdb fortran freetds freewnn ftp gb gcj gd gdbm geoip ggi gif ginac glut gmp gnome gnustep gnutls gphoto2 gpm gps gstreamer gtk gtk2 gtkhtml guile hal hardened hardenedphp howl hyperwave-api iconv icq imagemagick imap imlib inifile innodb interbase iodbc ipv6 jabber jack javascript joystick jpeg kde kerberos krb4 ladcca lcms ldap leim libcaca libg++ libgda libwww lirc lm_sensors lzw lzw-tiff m17n-lib mad maildir mailwrapper matroska mbox mcal mcve memlimit mhash migemo mikmod milter mime ming mmap mng mnogosearch motif mozilla mp3 mpeg mpi msession msql mssql mule mysql mysqli nas ncurses neXt netcdf nis nls nocd nptl oci8 odbc offensive ofx ogg openal opengl oracle oracle7 osc oscar oss ovrimos pam pcntl pcre pda pdflib perl php plotutils png portaudio posix postgres ppds prelude python qdbm qt quicktime readline recode ruby samba sapdb sasl scanner sdl session sharedext sharedmem shorten simplexml skey slang smartcard sndfile snmp soap sockets socks5 source sox speex spell spl sqlite ssl svg symlink sysvipc szip tcltk tcpd tetex theora threads tidy tiff tokenizer truetype truetype-fonts type1-fonts unicode usb userlocales v4l vcd vhosts videos vorbis wddx wifi wmf wxwindows xface xine xml xml2 xmlrpc xmms xosd xpm xprint xsl xv xvid yahoo yaz zeo zlib userland_GNU kernel_linux elibc_glibc" Unset: ASFLAGS, CTARGET, LDFLAGS, LINGUAS, PORTDIR_OVERLAY
You need to link with '-nopie'; GDB does not support PIEs (Position Independent Executables). Linking with '-nopie' means that the executable loads at the normal fixed address, and all symbols have real addresses. In a PIE, the load address is randomised at load time, and in the PIE itself all symbol addresses are offsets; gdb currently isn't clever enough to work this out. If you use PaX, in general you also need to do 'paxctl -mx' on the executable as well. $ gcc -ggdb3 -c x.c $ gcc -ggdb3 -nopie -o x-nopie x.c $ /sbin/paxctl -mx x-nopie $ gdb ./x-nopie GNU gdb 6.3 Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i686-pc-linux-gnu"...Using host libthread_db library "/lib/libthread_db.so.1". (gdb) run Starting program: /home/kquinn/x/x-nopie Program received signal SIGSEGV, Segmentation fault. 0x08048499 in main () at x.c:5 5 *ptr = 10; (gdb) bt full #0 0x08048499 in main () at x.c:5 ptr = (int *) 0x12345678 (gdb)
Ah yes, that works beautifully. I thank you, sir. Is this actually documented somewhere, or is one to discover this when one obtains useless backtraces? If one compiles a package with USE="debug" (and FEATURES="nostrip"), and still obtains these useless backtraces (like happened to me with KDevelop), is it a bug on a package-by-package basis, or are the useless backtraces the expected standard behavior when using a hardened Gentoo?
"Discover when faced with useless backtraces" is the usual method so far :) It's been in the forums a few times, probably also in the mailing lists, on IRC channels etc. I suppose it ought to be in the hardened FAQ; I'll see what I can do.
