[Bug libstdc++/40732] fstream get/put pointers have unexpected positions

["paolo dot carlini at oracle dot com" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #3 from paolo dot carlini at oracle dot com  2009-07-13 19:59 -------
The pointers are in some sense independent, but in this exact technical sense:
a seekg ends up calling the seekoff fstream virtual and therefore the mode
becomes 'uncommitted', neither read mode neither write mode. Successive writes
are therefore well defined and proceed exactly from the place where the last
read took place. Alternately, you could achieve the same net effect by stopping
reading when end of file is extracted: in C, and C++, this is a special case,
which also leads to 'uncommitted' mode, thus the following writes are well
defined - evidently in this case the user wants to append. But you can find
many testcases about all the various behaviors in the testsuite. Since this is
free software I also encourage you to browse the actual implementation: the
last special case, for example, is very clear toward the end of
basic_filebuf::underflow.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40732