search

babelouest / ulfius

Web Framework to build REST APIs, Webservices or any HTTP endpoint in C language. Can stream large amount of data, integrate JSON data with Jansson, and create websocket services
https://babelouest.github.io/ulfius
GNU Lesser General Public License v2.1
1.09k stars 182 forks source link

[Issue] gcc 14.2.1 warning #277

Open LaurentThomas opened 1 month ago

LaurentThomas commented 1 month ago

Hi,

gcc 14.2.1 refuse to compile:

The warning is quite bad, it says you test: if (data_len_in && data_len_in <= (SIZE_MAX-4)) but memcpy() max size is SSIZE_MAX (that is smaller)

possible fix: add #include and change the if to SSIZE_MAX

babelouest commented 1 month ago

Hello,

Thanks for reporting the issue. I've tried the suggested fix which does not break the tests, but I'm wondering if that's a good fix. In all the documentation I can find, it says that memcpy uses a size_t, I don't see that the max size is ssize_t anywhere.

I'm not suggesting it's a compiler bug but... Could it be a compiler bug?

Or more seriously, is there some memcpy documentation or limits I've missed somewhere?

LaurentThomas commented 1 month ago

Hi, Possibly It is Fedora 40 system, gcc version 14.2.1 20240801 (Red Hat 14.2.1-1) the full message is ulfius/src/u_websocket.c:2117:7: error: ‘memcpy’ specified size between 18446744073709551612 and 18446744073709551615 exceeds maximum object size 9223372036854775807 [-Werror=stringop-overflow=]

Nevertheless you are right, /usr/include/strings.h memcpy prototype is


extern void *memcpy (void *__restrict __dest, const void *__restrict __src,
                     size_t __n) __THROW __nonnull ((1, 2));

So, size_t (unsigned), not ssize_t (signed)

For this kind of issues, I don't add -Werror in my projects, even if i fully agree that authors must take care of warnings

babelouest commented 1 month ago

I've pushed the fix in the branch gcc-14.2.1-warning for now.

If the warning persists in the next gcc versions or appear in more cases, I'll merge the branch with master. I'll leave this issue open for now.

babelouest commented 3 weeks ago

Hello @LaurentThomas ,

I've seen this issue in other environments (Debian testing and Ubuntu 24.04 now).

Although, for some reason, the warning is raised when CMAKE_BUILD_TYPE=Debug (the default setup), but if I build with the cmake flag CMAKE_BUILD_TYPE=Release, the warning does not appear.

I don't know which one is right (I'm still wondering about the SSIZE_T check with memcpy), but it could be a workaround.