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fix integer overflow on i686 with high phys memory

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sizeof(long) is 4 bytes on i686 GCC.
With ~32 GiB of memory and a page size of 4096, there are 7988420 pages.
(7988420 * 4096) is bigger than INT32_MAX folks.

This has gone unnoticed for 9 years, and only came up thanks to
94ea517db[1] adding integer overflow sensitization checks, which caused
this broken code to emit an illegal instruction, crashing Lix the
instant the buildsystem ran Lix to generate the docs files.

[1]: 94ea517dbe729765b69638190f4bea3f6a632b40

Change-Id: I50bb9ea072aac11b449d79e5d55525887a6e5a99
This commit is contained in:
Qyriad 2024-05-05 13:18:59 -06:00
parent 4998699e1a
commit 99903f24eb
1 changed files with 6 additions and 5 deletions
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11
src/libexpr/eval.cc
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@ -316,13 +316,14 @@ void initGC()
(resident) memory to be allocated. This might be a problem on (resident) memory to be allocated. This might be a problem on
systems that don't overcommit. */ systems that don't overcommit. */
if (!getEnv("GC_INITIAL_HEAP_SIZE")) { if (!getEnv("GC_INITIAL_HEAP_SIZE")) {
size_t size = 32 * 1024 * 1024; int64_t size = 32 * 1024 * 1024;
#if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES) #if HAVE_SYSCONF && defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES)
size_t maxSize = 384 * 1024 * 1024; int64_t maxSize = 384 * 1024 * 1024;
long pageSize = sysconf(_SC_PAGESIZE); int64_t pageSize = sysconf(_SC_PAGESIZE);
long pages = sysconf(_SC_PHYS_PAGES); int64_t pages = sysconf(_SC_PHYS_PAGES);
if (pageSize != -1) if (pageSize != -1) {
size = (pageSize * pages) / 4; // 25% of RAM size = (pageSize * pages) / 4; // 25% of RAM
}
if (size > maxSize) size = maxSize; if (size > maxSize) size = maxSize;
#endif #endif
debug("setting initial heap size to %1% bytes", size); debug("setting initial heap size to %1% bytes", size);