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libstore: fix sign comparison warnings in darwin platform

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It's not clear to me if `proc_pidinfo()` or `proc_pidfdinfo()` can
actually return negative values, the syscall wrappers convert `-1` into
zero and the semantics suggest that negative values don't make sense,
but just to be safe we'll preserve the int type until we've checked that
it's a positive value.

Fixes: #548
Change-Id: If575aec6b1e27dba63091c7a0316c7b3788747cd
This commit is contained in:
Lily Ballard 2024-10-19 00:39:48 -07:00
parent 0ff8f91325
commit 068f4b147d
1 changed files with 10 additions and 6 deletions
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16
src/libstore/platform/darwin.cc
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@ -9,6 +9,7 @@
#include <libproc.h>
#include <spawn.h>
#include <cstddef>
#include <regex>
namespace nix {
@ -18,16 +19,17 @@ void DarwinLocalStore::findPlatformRoots(UncheckedRoots & unchecked)
auto storePathRegex = regex::storePathRegex(storeDir);
std::vector<int> pids;
int pidBufSize = 1;
std::size_t pidBufSize = 1;
while (pidBufSize > pids.size() * sizeof(int)) {
// Reserve some extra size so we don't fail too much
pids.resize((pidBufSize + pidBufSize / 8) / sizeof(int));
pidBufSize = proc_listpids(PROC_ALL_PIDS, 0, pids.data(), pids.size() * sizeof(int));
auto size = proc_listpids(PROC_ALL_PIDS, 0, pids.data(), pids.size() * sizeof(int));
if (pidBufSize <= 0) {
if (size <= 0) {
throw SysError("Listing PIDs");
}
pidBufSize = size;
}
pids.resize(pidBufSize / sizeof(int));
@ -53,12 +55,12 @@ void DarwinLocalStore::findPlatformRoots(UncheckedRoots & unchecked)
// File descriptors
std::vector<struct proc_fdinfo> fds;
int fdBufSize = 1;
std::size_t fdBufSize = 1;
while (fdBufSize > fds.size() * sizeof(struct proc_fdinfo)) {
// Reserve some extra size so we don't fail too much
fds.resize((fdBufSize + fdBufSize / 8) / sizeof(struct proc_fdinfo));
errno = 0;
fdBufSize = proc_pidinfo(
auto size = proc_pidinfo(
pid, PROC_PIDLISTFDS, 0, fds.data(), fds.size() * sizeof(struct proc_fdinfo)
);
@ -72,13 +74,15 @@ void DarwinLocalStore::findPlatformRoots(UncheckedRoots & unchecked)
// https://github.com/apple-opensource/xnu/blob/4f43d4276fc6a87f2461a3ab18287e4a2e5a1cc0/libsyscall/wrappers/libproc/libproc.c#L100-L110
// https://git.lix.systems/lix-project/lix/issues/446#issuecomment-5483
// FB14695751
if (fdBufSize <= 0) {
if (size <= 0) {
if (errno == 0) {
fdBufSize = 0;
break;
} else {
throw SysError("Listing pid %1% file descriptors", pid);
}
}
fdBufSize = size;
}
fds.resize(fdBufSize / sizeof(struct proc_fdinfo));