Bug ID: JDK-8205201 Problematic strncpy usage causes compiler warning on Fedora 28

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/home/pr/sources/jdk/src/hotspot/os/posix/os_posix.cpp: In static member function ���static int os::create_file_for_heap(const char*)���:
/home/pr/sources/jdk/src/hotspot/os/posix/os_posix.cpp:172:16: error: ���char* strncpy(char*, const char*, size_t)��� specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
   (void)strncpy(fullname, dir, strlen(dir)+1);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/pr/sources/jdk/src/hotspot/os/posix/os_posix.cpp:172:38: note: length computed here
   (void)strncpy(fullname, dir, strlen(dir)+1);
                                ~~~~~~^~~~~
/home/pr/sources/jdk/src/hotspot/os/posix/os_posix.cpp:173:16: error: ���char* strncat(char*, const char*, size_t)��� specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
   (void)strncat(fullname, name_template, strlen(name_template));
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors

It seems the limit is expected/required to be based on the size of the destination buffer rather than the source buffer. Which superficially seems reasonable, but it depends on whether you have sized your destination buffer based on the source size already. So these warnings could be false positives and we may need to make this a build issue and disable the warnings.

The current work-around is to configure with "--disable-warnings-as-errors".

05-07-2018

Note that one way to reproduce this warning is to use Fedora 28 and build OpenJDK. Fedora 28 has gcc 8.1.1: $ gcc --version gcc (GCC) 8.1.1 20180502 (Red Hat 8.1.1-1) Copyright (C) 2018 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See also: https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gcc/Warning-Options.html#index-Wstringop-overflow

19-06-2018