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Silent relocation truncations considered harmful
- From: Mark Geisert <mark at maxrnd dot com>
- To: cygwin-developers at cygwin dot com
- Date: Mon, 15 Feb 2016 18:23:30 -0800 (PST)
- Subject: Silent relocation truncations considered harmful
- Authentication-results: sourceware.org; auth=none
This follows up from my msg re GMP-ECM failing its 'make check' on the
main list https://cygwin.com/ml/cygwin/2016-02/msg00147.html .
There's an error that ought to be reported during dynamic linking if
the linked-to address is too far from the relocation site. However the
error is not reported if __OPTIMIZE__ was #defined when building the
Cygwin DLL. I can't see why optimization settings should affect this,
so I suggest:
/oss/src/winsup/cygwin diff -u pseudo-reloc.cc.safe pseudo-reloc.cc
--- pseudo-reloc.cc.safe 2016-01-26 20:08:06.000000000 -0800
+++ pseudo-reloc.cc 2016-02-15 17:54:20.475963800 -0800
@@ -342,7 +342,7 @@
__write_memory ((void *) reloc_target, &reldata, 2);
break;
case 32:
-#if defined (__CYGWIN__) && defined (__x86_64__) && !defined (__OPTIMIZE__)
+#if defined (__CYGWIN__) && defined (__x86_64__)
if (reldata > (ptrdiff_t) __INT32_MAX__
|| reldata < -((ptrdiff_t) __INT32_MAX__) - 1)
__report_error ("Invalid relocation. Offset %p at address %p "
If the truncation is not reported here, which kills the program with a
Cygwin runtime error, you get hard to diagnose SIGSEGVs at some later time
when the app tries to call a function at an address relocated off in the
weeds somewhere.
..mark