#7072: GHC interpreter does not find stat64 symbol on Linux
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Reporter: snoyberg | Owner:
Type: bug | Status: new
Priority: normal | Component: GHCi
Version: 7.4.2 | Keywords:
Os: Linux | Architecture: x86_64 (amd64)
Failure: GHCi crash | Testcase:
Blockedby: | Blocking:
Related: |
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Mailing list discussion available at: [
http://www.haskell.org/pipermail /haskell-cafe/2012-July/102253.html]. The issue is that, when using runghc
against a library using the sqlite3 C library (persistent-sqlite), the
stat64 symbol is not resolved. After some research, I came up with the
following minimal reproducing 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");
}
}}}
When using stat directly, gcc inlines the call and produces assembly which
simply makes a system call, thereby avoiding the need for the stat symbol.
However, when using a function pointer (as sqlite3 does), the symbol is
retained, and then runghc does not resolve it.
In the linked mailing list discussion, Tristan Ravitch found a Stack
Overflow thread ([
http://stackoverflow.com/questions/5478780/c-and-ld- preload-open-and-open64-calls-intercepted-but-not-stat64]) which explains
that the GNU linker has special handling for the stat, stat64, and a few
other library functions. glibc itself does not provide those symbols
directly, relying on the linker to fix the references. (I could not find
reference to this in any official documentation.)
As a workaround, I declared some local functions which call stat and
stat64 (patch available at
[
https://github.com/yesodweb/persistent/commit/d7daf0b2fa401fd97ef62e4e74228146d15d8601]).
So there is a workaround available, and therefore this isn't high priority
for me. But I do think it's worth some kind of fix.
Without having a good understanding of the GHC interpreter, my guess would
be that it needs to replicate the stat/stat64/etc hack that the GNU linker
is performing. Of course, this guess may be incorrect.
Tested on Ubuntu 12.04 64-bit, though I believe it will affect any recent
version of Linux, whether 32- or 64-bit.
--
Ticket URL: <
http://hackage.haskell.org/trac/ghc/ticket/7072>
GHC <
http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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