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From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050513 Fedora/1.0.4-1.3.1 Firefox/1.0.4 Description of problem: Simply reading or writing to the h_errno global variable gives out a read/write violation in mudflap. Version-Release number of selected component (if applicable): glibc-2.3.5-10 How reproducible: Always Steps to Reproduce: 1. Compile the program #include <stdio.h> #include <netdb.h> int main() { printf("%d", h_errno); return 0; } and the program #include <netdb.h> int main() { h_errno = 0; return 0; } with mudflap enabled, i.e. gcc -fmudflap prog1.c -lmudflap -o prog1 and gcc -fmudflap prog2.c -lmudflap -o prog2 2. Run prog1 and prog2. Actual Results: When prog1 is run, this is what I get: ******* mudflap violation 1 (check/read): time=1121380261.574621 ptr=0xb7eff6b4 size=4 pc=0xb7f09322 location=`a.cpp:6 (main)' /usr/lib/libmudflap.so.0(__mf_check+0x44) [0xb7f09322] ./a.out(main+0x81) [0x8048839] /usr/lib/libmudflap.so.0(__wrap_main+0x1d8) [0xb7f0a04e] Nearby object 1: checked region begins 17B after and ends 20B after mudflap object 0x80cb430: name=`errno area' bounds=[0xb7eff6a0,0xb7eff6a3] size=4 area=static check=0r/0w liveness=0 alloc time=1121380261.574591 pc=0xb7f09e0a number of nearby objects: 1 When prog2 is run, the report is similar, but it says "(check/write)", instead of "(check/read)" -- because h_errno is written to. Expected Results: There should have been no violation messages. Additional info:
That's a mudflap bug. (*__h_errno_location()) (which is what h_errno expands to) is a thread local storage variable similarly to errno (*__errno_location()). libmudflap has special quirks for errno, but not for h_errno (and I guess not for _res either, and I wonder if any other thread local storage variable).
Jakub, cool, thanks! May I ask why the need for h_errno to expand to a thread local storage variable if gethostbyname is not reentrant, and it (global h_errno) isn't used by the reentrant equivalent gethostbyname_r?
h_errno is used in many other functions, some of which are reentrant.
Is there a complete list of such variables someplace? Failing that, I'll add h_errno support to gcc mainline, and consider backporting.
mudflap is very buggy atm, i get violations just reading from argv[] :)
(In reply to comment #5) > mudflap is very buggy atm, i get violations just reading from argv[] :) This would be a separate problem. Make sure you pass -fmudflap to the link stage too. If you do, and you still encounter this, please open a separate bugzilla with a sample program.
This report targets the FC3 or FC4 products, which have now been EOL'd. Could you please check that it still applies to a current Fedora release, and either update the target product or close it ? Thanks.
this bug is still present in Fedora 8, gcc-4.1.2-33
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Fedora 8 changed to end-of-life (EOL) status on 2009-01-07. Fedora 8 is no longer maintained, which means that it will not receive any further security or bug fix updates. As a result we are closing this bug. If you can reproduce this bug against a currently maintained version of Fedora please feel free to reopen this bug against that version. Thank you for reporting this bug and we are sorry it could not be fixed.