#10093: Library configure scripts should not clobber CPPFLAGS nor LDFLAGS -------------------------------------+------------------------------------- Reporter: PHO | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build | Version: 7.11 System | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime crash Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- `libraries/base/configure` currently clobbers `CPPFLAGS` and `LDFLAGS` when `--with-iconv-includes` and `--with-iconv-libraries` are given, but really it shouldn't. I will soon submit a patch for this. Here's what I stumbled upon (TL;DR): This is somewhat related to #2933. I have libiconv installed in `/usr/pkg`, which is a non-standard path that `ld.so` normally doesn't search libraries for. So I built GHC with `CONF_GCC_LINKER_OPTS_STAGE{0,1,2}` set to `-Wl,-rpath,/usr/pkg/lib` so that GHC links executables with `RPATH` pointing to `/usr/pkg/lib`. The build went fine until it started using `ghc-stage2` and `haddock`: they were causing segfaults in `evacuate()` with a probability of about 70%, which suggested a heap corruption occuring somewhere. I tried rebuilding RTS with `-O0 -g`, changed various parameters for GC, etc. Nothing changed. Then I suddenly realized that `libraries/base/configure` was the root cause of the problem. Those `configure` scripts are executed with `LDFLAGS` being set to the value of `CONF_GCC_LINKER_OPTS_STAGE2`, which is `-Wl,-rpath,/usr/pkg/lib` in my case, but `libraries/base/configure` overwrites it to `-L/usr/pkg/lib` when `--with-iconv- libraries=/usr/pkg/lib` is given. On the other hand, `FP_SEARCH_LIBS_PROTO(iconv)` appends `-liconv` to `$LIBS` so it will be linked to any conftest executables that follow, including one which will be generated by `AC_CHECK_SIZEOF()`. The problem is that if libraries listed in `$LIBS` are in a non-standard path while rpath flags are missing (due to `LDFLAGS` being clobbered in this case), conftest executables cannot run even if they can be linked. And if anything goes wrong during `AC_CHECK_SIZEOF(T)`, it considers `sizeof(T)` as 0 unless `T` is known to be an existing type: {{{ ... checking for library containing iconv... -liconv checking for library containing locale_charset... none required checking size of struct MD5Context... 0 ... }}} This means `SIZEOF_STRUCT_MD5CONTEXT` gets defined to 0, `GHC.Fingerprint.fingerprintData` allocates 0 bytes on the heap, `MD5Init`/`Update`/`Final` corrupts the heap and then Bad Things will happen. I have found the problem on NetBSD/amd64 but I'm sure the same thing happens on every ELF platform. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10093 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler