Building with Clang 16 fails with sign-compare about unit HOT 13 CLOSED

That's their perogative. I don't see a compelling reason why we shouldn't.

from unit.

Lets move this to a separate issue...

from unit.

A long known issue between musl libc and clang.

One way to workaround this would be to create our own wrapper around CMSG_NXTHDR and do the #pragma thing...

Something like the following perhaps...

diff --git a/src/nxt_socket_msg.h b/src/nxt_socket_msg.h
index 04de1761..fca82f05 100644
--- a/src/nxt_socket_msg.h
+++ b/src/nxt_socket_msg.h
@@ -69,6 +69,19 @@ NXT_EXPORT ssize_t nxt_recvmsg(nxt_socket_t s,
     nxt_iobuf_t *iob, nxt_uint_t niob, nxt_recv_oob_t *oob);
 
 
+static inline struct cmsghdr *
+NXT_CMSG_NXTHDR(struct msghdr *msg, struct cmsghdr *cmsg)
+{
+#ifndef __GLIBC__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wsign-compare"
+#endif
+    return CMSG_NXTHDR(msg, cmsg);
+#ifndef __GLIBC__
+#pragma clang diagnostic pop
+#endif
+}
+
 nxt_inline void
 nxt_socket_msg_oob_init(nxt_send_oob_t *oob, int *fds)
 {
@@ -135,7 +148,7 @@ nxt_socket_msg_oob_get_fds(nxt_recv_oob_t *oob, nxt_fd_t *fd
)
 
     for (cmsg = CMSG_FIRSTHDR(&msg);
          cmsg != NULL;
-         cmsg = CMSG_NXTHDR(&msg, cmsg))
+         cmsg = NXT_CMSG_NXTHDR(&msg, cmsg))
     {
         size = cmsg->cmsg_len - CMSG_LEN(0);
 
@@ -174,7 +187,7 @@ nxt_socket_msg_oob_get(nxt_recv_oob_t *oob, nxt_fd_t *fd, nx
t_pid_t *pid)
 
     for (cmsg = CMSG_FIRSTHDR(&msg);
          cmsg != NULL;
-         cmsg = CMSG_NXTHDR(&msg, cmsg))
+         cmsg = NXT_CMSG_NXTHDR(&msg, cmsg))
     {
         size = cmsg->cmsg_len - CMSG_LEN(0);
 

from unit.

Hi,

@ac000 @andypost
Could you try NGINX with the same OS?

> git clone https://github.com/nginx/nginx.git
> cd nginx
> ./auto/configure && make

@andrey-zelenkov Do we need to add it to BB?

from unit.

nginx has the same issue

$ auto/configure --with-cc=clang && make -j4
...
clang -c -pipe  -O -Wall -Wextra -Wpointer-arith -Wconditional-uninitialized -Wno-unused-parameter -Werror -g  -I src/core -I src/event -I src/event/modules -I src/event/quic -I src/os/unix -I objs \
        -o objs/src/event/ngx_event_connect.o \
        src/event/ngx_event_connect.c
src/event/ngx_event_udp.c:143:25: error: comparison of integers of different signs: 'unsigned long' and 'long' [-Werror,-Wsign-compare]
                 cmsg = CMSG_NXTHDR(&msg, cmsg))
                        ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/sys/socket.h:358:44: note: expanded from macro 'CMSG_NXTHDR'
        __CMSG_LEN(cmsg) + sizeof(struct cmsghdr) >= __MHDR_END(mhdr) - (unsigned char *)(cmsg) \
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

from unit.

Good catch, thanks.

from unit.

See https://trac.nginx.org/nginx/ticket/2534 for the related issue in nginx. They decided not to fix that.

from unit.

@ac000 thank you for patch! it allows to build meantime exposed issues on armv7 and armv8 and riscv64

checking for GCC __builtin_expect() ... not found
checking for GCC __builtin_unreachable() ... not found
checking for GCC __builtin_prefetch() ... not found
checking for GCC __builtin_clz() ... not found
checking for GCC __builtin_popcount() ... not found
checking for GCC __attribute__ visibility ... not found
checking for GCC __attribute__ aligned ... not found
checking for GCC __attribute__ malloc ... not found
checking for GCC __attribute__ packed ... not found
checking for GCC __attribute__ unused ... not found
checking for GCC builtin atomic operations ... not found
checking for Solaris builtin atomic operations ... not found
checking for xlC builtin atomic operations ... not found
./configure: error: no atomic operations found.

maybe it's related to clang for this arches but at least "GCC" prefix for atomics is confusing when building with clang

from unit.

Using clang 15.0.7 I'm getting the same error

from unit.

@andypost

Thanks for testing.

@ac000 thank you for patch! it allows to build meantime exposed issues on armv7 and armv8 and riscv64

checking for GCC __builtin_expect() ... not found
checking for GCC __builtin_unreachable() ... not found
checking for GCC __builtin_prefetch() ... not found
checking for GCC __builtin_clz() ... not found
checking for GCC __builtin_popcount() ... not found
checking for GCC __attribute__ visibility ... not found
checking for GCC __attribute__ aligned ... not found
checking for GCC __attribute__ malloc ... not found
checking for GCC __attribute__ packed ... not found
checking for GCC __attribute__ unused ... not found
checking for GCC builtin atomic operations ... not found
checking for Solaris builtin atomic operations ... not found
checking for xlC builtin atomic operations ... not found
./configure: error: no atomic operations found.

maybe it's related to clang for this arches but at least "GCC" prefix for atomics is confusing when building with clang

Hmm, we just have the three above checks here, one for GCC 4.1+ (heh, I'm just quoting the auto/atomic script), Solaris 10 & AIX xlC. The mind boggles, I suspect these just came straight from nginx...

It's also weird that it failed to find all the builtins and attributes...

I assume GCC builds Unit fine on such systems?

Some more investigation is probably required...

from unit.

Yes, using GCC it builds/works fine, I just attempted to use clang to see effect

from unit.

Thanks for confirming.

No, sure, while GCC is my compiler of choice I see value in also testing with clang, they both find different issues in code.

from unit.

Fix was committed.

from unit.