GitLab

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.

Trac metadata

Trac field	Value
Version	7.4.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture