Simone Caronni created GUACAMOLE-720:
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Summary: Build failure with GCC 9
Key: GUACAMOLE-720
URL: https://issues.apache.org/jira/browse/GUACAMOLE-720
Project: Guacamole
Issue Type: Bug
Components: guacd
Affects Versions: 1.0.0
Reporter: Simone Caronni
In particular GCC 9 complains about this code:
{code}
> BUILDSTDERR: In file included from /usr/include/string.h:494,
> BUILDSTDERR: from /usr/include/winpr/collections.h:25,
> BUILDSTDERR: from /usr/include/freerdp/types.h:80,
> BUILDSTDERR: from /usr/include/freerdp/svc.h:24,
> BUILDSTDERR: from /usr/include/freerdp/utils/svc_plugin.h:27,
> BUILDSTDERR: from ./rdp_svc.h:25,
> BUILDSTDERR: from guac_svc/svc_service.h:24,
> BUILDSTDERR: from guac_svc/svc_service.c:22:
> BUILDSTDERR: In function 'strncpy',
> BUILDSTDERR: inlined from 'VirtualChannelEntry' at
> guac_svc/svc_service.c:56:5:
> BUILDSTDERR: /usr/include/bits/string_fortified.h:106:10: error:
> '__builtin_strncpy' output may be truncated copying 7 bytes from a string of
> length 7 [-Werror=stringop-truncation]
> BUILDSTDERR: 106 | return __builtin___strncpy_chk (__dest, __src, __len,
> __bos (__dest));
> BUILDSTDERR: |
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> BUILDSTDERR: cc1: all warnings being treated as errors
{code}
Which stems from this code:
{code}
> /* Init channel def */
>
>strncpy(svc_plugin->[plugin.channel_def.name|http://plugin.channel_def.name/],
>svc->name,
> GUAC_RDP_SVC_MAX_LENGTH);
{code}
The compiler is complaining because it can not prove the resulting string has a
proper NUL terminator. This can cause runtime faults and even security issues.
Most folks are fixing this by either NUL terminating the string after the call
to strncpy . However, in some cases the string is not guaranteed to be NUL
terminated -- in those cases the "nonstring" attribute is more appropriate.
Note that using "nonstring" will cause the compiler to analyze use points and
warn if you pass a "nonstring" variable to a routine that expects a properly
terminated NUL string such as strlen.
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