Bip

So the Red Hat compiler team very kindly pre-checked build of a bunch of Fedora packages with GCC 9 (which will be showing up in Fedora Rawhide soon), and they flagged up two issues in Bip which will cause it to fail to build with GCC 9. This is the first issue.

I'll just paste Jeff Law's explanation here, because he explains it much better than I could:

gcc -DHAVE_CONFIG_H -I. -I./src    -Wall -Wextra -Werror -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fPIE -Wno-unused-result -Wno-error=format-truncation -c -o src/log.o src/log.c
BUILDSTDERR: In file included from /usr/include/string.h:494,
BUILDSTDERR:                  from src/connection.h:26,
BUILDSTDERR:                  from src/irc.h:16,
BUILDSTDERR:                  from src/log.c:18:
BUILDSTDERR: In function 'strncpy',
BUILDSTDERR:     inlined from 'check_dir_r' at src/log.c:87:5:
BUILDSTDERR: /usr/include/bits/string_fortified.h:106:10: error: '__builtin_strncpy' output truncated before terminating nul copying 1 byte from a string of the same length [-Werror=stringop-truncation]
BUILDSTDERR:   106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
BUILDSTDERR:       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUILDSTDERR: src/log.c: In function 'log_build_filename':
BUILDSTDERR: src/log.c:148:21: warning: '%04d' directive output may be truncated writing between 4 and 11 bytes into a region of size 5 [-Wformat-truncation=]
BUILDSTDERR:   148 |  snprintf(year, 5, "%04d", now->tm_year + 1900);
BUILDSTDERR:       |                     ^~~~
BUILDSTDERR: src/log.c:148:20: note: directive argument in the range [-2147481748, 2147483647]
BUILDSTDERR:   148 |  snprintf(year, 5, "%04d", now->tm_year + 1900);
BUILDSTDERR:       |                    ^~~~~~
BUILDSTDERR: In file included from /usr/include/stdio.h:867,
BUILDSTDERR:                  from src/log.h:17,
BUILDSTDERR:                  from src/log.c:17:
BUILDSTDERR: /usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk' output between 5 and 12 bytes into a destination of size 5
BUILDSTDERR:    67 |   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
BUILDSTDERR:       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUILDSTDERR:    68 |        __bos (__s), __fmt, __va_arg_pack ());
BUILDSTDERR:       |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUILDSTDERR: src/log.c:150:22: warning: '%02d' directive output may be truncated writing between 2 and 11 bytes into a region of size 3 [-Wformat-truncation=]
BUILDSTDERR:   150 |  snprintf(month, 3, "%02d", now->tm_mon + 1);
BUILDSTDERR:       |                      ^~~~
BUILDSTDERR: src/log.c:150:21: note: directive argument in the range [-2147483647, 2147483647]
BUILDSTDERR:   150 |  snprintf(month, 3, "%02d", now->tm_mon + 1);
BUILDSTDERR:       |                     ^~~~~~
BUILDSTDERR: In file included from /usr/include/stdio.h:867,
BUILDSTDERR:                  from src/log.h:17,
BUILDSTDERR:                  from src/log.c:17:
BUILDSTDERR: /usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk' output between 3 and 12 bytes into a destination of size 3
BUILDSTDERR:    67 |   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
BUILDSTDERR:       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUILDSTDERR:    68 |        __bos (__s), __fmt, __va_arg_pack ());
BUILDSTDERR:       |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUILDSTDERR: cc1: all warnings being treated as errors
make[1]: Leaving directory '/builddir/build/BUILD/bip-0.9.0-rc3'
RPM build errors:

SO the first error is the easiest to deal with. In check_dir_r we have:

while (*tmp == '/') {
                        if (slash_ok) {
                                strncpy(dir + count, "/", 1);
                                count++;
                                slash_ok = 0;
                        }
                        tmp++;
                }

Note the code is using a strncpy to copy a single constant byte without NUL termination. That's wasteful and runs afoul of gcc-9's attempts to track when the destination is not going to properly terminated.

Our recommendation is to replace the strncpy call with

dir[count] = '/';