Linux kernel quiz: Why is this program so slow and takes around 50ms to run?
What line do you have to add to make it run in ~3ms instead without interfering with what this program does?

user@debian12:~/test$ cat > slow.c
#include <pthread.h>
#include <unistd.h>
#include <err.h>
#include <sys/socket.h>

static void open_sockets(void) {
  for (int i=0; i<256; i++) {
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == -1)
      err(1, "socket");
  }
}

static void *thread_fn(void *dummy) {
  open_sockets();
  return NULL;
}

int main(void) {
  pthread_t thread;
  if (pthread_create(&thread, NULL, thread_fn, NULL))
    errx(1, "pthread_create");
  open_sockets();
  if (pthread_join(thread, NULL))
    errx(1, "pthread_join");
  return 0;
}
user@debian12:~/test$ gcc -O2 -o slow slow.c -Wall
user@debian12:~/test$ time ./slow

real    0m0.041s
user    0m0.003s
sys     0m0.000s
user@debian12:~/test$ time ./slow

real    0m0.053s
user    0m0.003s
sys     0m0.000s
user@debian12:~/test$

anyone know how to get around this compilation fail on Solaris?

In file included from pkg_libecc_rand.c:6:
/usr/share/src/fractal/build/progress/pkg-2.2.1/compat/bsd_compat.h:188:3: error: #error "Your system has neither funopen nor fopencookie, cannot continue"
188 | # error "Your system has neither funopen nor fopencookie, cannot continue"
| ^~~~~
/usr/share/src/fractal/build/progress/pkg-2.2.1/compat/bsd_compat.h:190:1: error: unknown type name 'FILE'
190 | FILE * funopen(const void *cookie, int (*readfn)(void *, char *, int),
| ^~~~
/usr/share/src/fractal/build/progress/pkg-2.2.1/compat/bsd_compat.h:97:1: note: 'FILE' is defined in header '<stdio.h>'; did you forget to '#include <stdio.h>'?
96 | #include "humanize_number.h"
+++ |+#include <stdio.h>
97 | #endif
/usr/share/src/fractal/build/progress/pkg-2.2.1/compat/bsd_compat.h:203:4: error: #error "Don't know how to replace getprogname()"
203 | # error "Don't know how to replace getprogname()"
| ^~~~~

Retro C++ quiz #33

#include <iostream>

int main(){
char arr[] = "junk";
char c{'a'};

std::cout << &c; // What will this likely output?
}

Without checking:

A. some valid address e.g. 0x7ffc6a86d386
B. a
C. 97
D. ¯\_(ツ)_/¯ Undefined behavior

#Cplusplus
#Cpppolls

Social media tip: If you look for hashtag #include, you get some fun toots about C/C++

This was fun - missing.c:

#include <stdio.h>
#include <stdlib.h>

void die(int err, char *msg) {
err? fprintf(stderr, "%s\n", msg), exit(1): 0;
}

int main(int argc, char *argv[]) {
int n, answer = 1, val;

die(argc != 2 || (n = atoi(argv[1])) < 2, "Usage: missing n");
for (; n > 1; n--) {
die(scanf("%d", &val) != 1, "Error reading input");
answer ^= val ^ n;
}
printf("%d\n", answer);
}

justine@justine@snac.smithies.me.uk-laptop ~/Git/mmsg  main $ doas make install
Password:
cc  -O2 -pipe `pkg-config --cflags wayland-client -lcjson` -c mmsg.c -o mmsg.o
pkgconf: unknown option -- lcjson
In file included from mmsg.c:2:
./dwl-ipc-unstable-v2-protocol.h:8:10: fatal error: 'wayland-client.h' file not found
    8 | #include "wayland-client.h"
      |          ^~~~~~~~~~~~~~~~~~
1 error generated.
*** Error code 1

Stop.
make: stopped in /home/justine/Git/mmsg

@doctormo Is it "raw artisanal hand-written ninja" or "cmake-generated ninja"? For the latter:

$ rm compile_commands.json # just in case
$ cat CMakeLists.txt
cmake_minimum_required(VERSION 3.5)
project(test)
add_executable(test test.c)
$ cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -GNinja .
$ ninja
[2/2] Linking C executable test
$ iwyu-tool -p . test.c
/tmp/test.c should add these lines:

/tmp/test.c should remove these lines:
- #include <stddef.h> // lines 2-2

@doctormo I see. It's possible to "untie from the build system" using https://github.com/rizsotto/Bear:

$ cat test.c
#include <stdio.h>
#include <stddef.h>
int main() { printf("hello"); }
$ bear -- gcc test.c
$ iwyu-tool -p . test.c
test.c should add these lines:

test.c should remove these lines:
- #include <stddef.h> // lines 2-2

The full include-list for test.c:
#include <stdio.h> // for printf

#include #inclusion https://alberta.nyc/

#Recursion

When I do it:

#include <stdio.h>
long int factorial(int number) {
if(number >= 1)
return number*factorial(number-1);
else
return 1;
}

When #DollarGeneral does it:

We wrote our first shared library today! libflock, implements fllock() and friends on Solaris by using fcntl, #include <flock.h> and add -lflock to LDFLAGS. Fixes @grunfink's snac2 and other tools not building due to incorrect locking. Will be up on our git later today. GPL2 licensed.