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Overview
Comment: | Provide an alternative "guaranteed-safe" method for overwriting the WAL index on recovery, in case some platform is found for which memcpy() cannot do this safely. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA3-256: |
168cccbabbd4807bdb04953f395cd1a2 |
User & Date: | drh 2020-07-30 22:33:36.214 |
Context
2020-07-30
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23:47 | Test for schema corruption is reachable after all. (check-in: 2032236cce user: drh tags: trunk) | |
22:33 | Provide an alternative "guaranteed-safe" method for overwriting the WAL index on recovery, in case some platform is found for which memcpy() cannot do this safely. (check-in: 168cccbabb user: drh tags: trunk) | |
17:37 | Fix compiler warnings in MSVC. (check-in: 96e3dba2ed user: drh tags: trunk) | |
Changes
Changes to src/wal.c.
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1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 | aFrameCksum[0] = pWal->hdr.aFrameCksum[0]; aFrameCksum[1] = pWal->hdr.aFrameCksum[1]; } } pWal->apWiData[iPg] = aShare; nHdr = (iPg==0 ? WALINDEX_HDR_SIZE : 0); nHdr32 = nHdr / sizeof(u32); memcpy(&aShare[nHdr32], &aPrivate[nHdr32], WALINDEX_PGSZ-nHdr); if( iFrame<=iLast ) break; } sqlite3_free(aFrame); } finished: | > > > > > > > > > > > > > > > > > > > > > > > > > > > | 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 | aFrameCksum[0] = pWal->hdr.aFrameCksum[0]; aFrameCksum[1] = pWal->hdr.aFrameCksum[1]; } } pWal->apWiData[iPg] = aShare; nHdr = (iPg==0 ? WALINDEX_HDR_SIZE : 0); nHdr32 = nHdr / sizeof(u32); #ifndef SQLITE_SAFER_WALINDEX_RECOVERY /* Memcpy() should work fine here, on all reasonable implementations. ** Technically, memcpy() might change the destination to some ** intermediate value before setting to the final value, and that might ** cause a concurrent reader to malfunction. Memcpy() is allowed to ** do that, according to the spec, but no memcpy() implementation that ** we know of actually does that, which is why we say that memcpy() ** is safe for this. Memcpy() is certainly a lot faster. */ memcpy(&aShare[nHdr32], &aPrivate[nHdr32], WALINDEX_PGSZ-nHdr); #else /* In the event that some platform is found for which memcpy() ** changes the destination to some intermediate value before ** setting the final value, this alternative copy routine is ** provided. */ { int i; for(i=nHdr32; i<WALINDEX_PGSZ/sizeof(u32); i++){ if( aShare[i]!=aPrivate[i] ){ /* Atomic memory operations are not required here because if ** the value needs to be changed, that means it is not being ** accessed concurrently. */ aShare[i] = aPrivate[i]; } } } #endif if( iFrame<=iLast ) break; } sqlite3_free(aFrame); } finished: |
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