BUG #18991: NUMA test fails on machine with two NUMA nodes when building 18beta2

The following bug has been logged on the website:

Bug reference:      18991
Logged by:          Maximilian Bosch
Email address:      maximilian@mbosch.me
PostgreSQL version: 18beta2
Operating system:   NixOS 25.11 / unstable
Description:

Hi!

On NixOS master/unstable we provide betas of PostgreSQL to enable people
such as extension devs to quickly identify problems with it.

When building 18beta2 with `--with-libnuma` and linking against libnuma.so
from numactl 2.0.18, I get the following test failure while building the
package on a machine with two NUMA nodes:

```
diff -U3 /build/source/src/test/regress/expected/numa.out
/build/source/src/test/regress/results/numa.out
--- /build/source/src/test/regress/expected/numa.out    1970-01-01
00:00:01.000000000 +0000
+++ /build/source/src/test/regress/results/numa.out     2025-07-19
08:44:02.793368816 +0000
@@ -6,8 +6,4 @@
 -- switch to superuser
 \c -
 SELECT COUNT(*) >= 0 AS ok FROM pg_shmem_allocations_numa;
- ok
-----
- t
-(1 row)
-
+ERROR:  invalid NUMA node id outside of allowed range [0, 0]: 1
```

As mentioned above, the machine I used to build things has two NUMA nodes.
`numactl --hardware` gives

```
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73
74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 192 193
194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212
213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231
232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250
251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269
270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287
node 0 size: 773538 MB
node 0 free: 603763 MB
node 1 cpus: 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112
113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131
132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169
170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188
189 190 191 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303
304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322
323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341
342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360
361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379
380 381 382 383
node 1 size: 767886 MB
node 1 free: 667997 MB
node distances:
node   0   1
  0:  10  32
  1:  32  10
```

I'm aware that there was already discussion about this in
https://www.postgresql.org/message-id/flat/E1u1tr8-003BbN-2E%40gemulon.postgresql.org,
but it seems like this was a different issue given that an error-code was
given instead of an actual NUMA id? Also, all of the discussion including a
fix seem to have happened well before 18beta2, hence I'm filing a new
report.

Relevant downstream discussions:
* https://github.com/NixOS/nixpkgs/pull/411958#issuecomment-3031660150
* https://github.com/NixOS/nixpkgs/pull/426118

Let me know if I can help with something, e.g. testing potential fixes.

Best
Ma27