Date: Fri, 17 May 2013 13:37:10 -0400 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Broken silent glibc-specific assumptions uncovered by musl Hi all, There's been at least one request for putting together a list of "silent" application bugs uncovered by building against musl applications which were previously used mainly/only with glibc. By silent, I mean things that are not easily caught as configure- or compile-time errors, but which cause the application to misbehave at runtime. I'm writing down here what I can think of off-hand. This list should probably be expanded by the community and perhaps put on the wiki. Here's what I have so far: Assuming that dlerror is thread-local. (POSIX previously required it to be global; as of 2008-TC1, either behavior is allowed.) Assuming dlclose actually unloads a library (and calls dtors), so that a future dlopen will reset static objects to their initial state (and re-run ctors). (POSIX leaves this implementation-defined, and unloading is impossible to do safely in general, so robust implementations will not do it.) Making wrong assumptions about fsync and fdatasync. (I'm not familiar with this issue so somebody else will have to fill it in.) Calling exit from global destructors. (If an application calls exit more than once, the behavior is undefined.) Assuming pthread_cancel unwinds and calls destructors. (Interaction between cancellation and C++ is undefined.) Use of GNU extensions in regular expressions, especially backslash-prefixed versions of ERE operators in BRE. (Undefined.) Assuming iconv reports characters that cannot be represented in the dest charset via EILSEQ. (This behavior is non-conforming; POSIX requires an implementation-defined replacement and positive return value in this case.) Use of deprecated charset aliases with iconv_open, for example, using "UNICODE" to mean UCS-2. (The list of charsets is implementation-defined, but common sense dictates using the IANA preferred MIME charset names, and especially not misleading names.)
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