[Haskell-cafe] ghci and TH cannot: unknown symbol `stat64`

[Michael Snoyman]

On Thu, Jul 12, 2012 at 7:07 PM, Tristan Ravitch <travitch at cs.wisc.edu>wrote:

> On Thu, Jul 12, 2012 at 06:29:41PM +0300, Michael Snoyman wrote:
> > I've come up with a minimal example that demonstrates this problem. The
> > crux of the matter is the following C code:
> >
> >     #include <sys/types.h>
> >     #include <sys/stat.h>
> >     #include <unistd.h>
> >     #include <stdio.h>
> >
> >     typedef int stat_func(const char*, struct stat*);
> >
> >     stat_func *foo = &stat;
> >
> >     void stat_test(void)
> >     {
> >     struct stat buf;
> >
> >     printf("About to stat-test.c\n");
> >     foo("stat-test.c", &buf);
> >     printf("Done\n");
> >     }
> >
> > As you can see, all of the include statements are present as necessary.
> The
> > code compiles just fine with -Wall -Werror. And when you compile the
> > Haskell code as well, everything works just fine. But if you follow these
> > steps, you can reproduce the error I saw:
> >
> > * Unpack the attached tarball
> > * `cabal install` in that folder
> > * `runghc main.hs` from the `exe` folder
> >
> > On my system at least, I get:
> >
> >     main.hs:
> >
> /home/ubuntu/.cabal/lib/stat-test-0.1.0.0/ghc-7.4.1/HSstat-test-0.1.0.0.o:
> > unknown symbol `stat'
> >     main.hs: main.hs: unable to load package `stat-test-0.1.0.0'
> >
> > One thing I noticed is that I needed to use a function pointer to trigger
> > the bug. When I called `stat` directly the in stat_test function, gcc
> > automatically inlined the call, so that the disassessmbled code just
> showed
> > a `moveq` (i.e., it's making the system call directly). But using a
> > function pointer, we're avoiding the inlining. I believe this is why this
> > issue only came up with the sqlite3 upgrade: previous versions did not
> use
> > a function pointer, but rather hard-coded in how to make a stat call.
> >
> > Does this expose any other possibilities?
> >
> > Michael
>
> Are you trying this on a 32 bit system?  And when you compiled that C
> program, did you try to add
>
>   -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE
>
> to the compile command?  When I define those the resulting object file
> from your example correctly references stat64 instead of stat.
>

I'm compiling on a 64 bit system. If I add those definitions, the program
uses stat64 instead, but the only difference is that runghc now prints:

    main.hs:
/home/ubuntu/.cabal/lib/stat-test-0.1.0.0/ghc-7.4.1/HSstat-test-0.1.0.0.o:
unknown symbol `stat64'
    main.hs: main.hs: unable to load package `stat-test-0.1.0.0'

In other words, it's not the symbol that the object file is referencing
(stat vs stat64) that's the problem: runghc is not able to resolve either
one.

Michael
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