2cd468874f
Because config.h can #define things like _FILE_OFFSET_BITS=64 and not
every compilation unit includes config.h, we currently compile half of
Nix with _FILE_OFFSET_BITS=64 and other half with _FILE_OFFSET_BITS
unset. This causes major havoc with the Settings class on e.g. 32-bit ARM,
where different compilation units disagree with the struct layout.
E.g.:
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
@@ -166,6 +166,8 @@ void Settings::update()
_get(useSubstitutes, "build-use-substitutes");
+ fprintf(stderr, "at Settings::update(): &useSubstitutes = %p\n", &nix::settings.useSubstitutes);
_get(buildUsersGroup, "build-users-group");
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -138,6 +138,8 @@ void RemoteStore::initConnection(Connection & conn)
void RemoteStore::setOptions(Connection & conn)
{
+ fprintf(stderr, "at RemoteStore::setOptions(): &useSubstitutes = %p\n", &nix::settings.useSubstitutes);
conn.to << wopSetOptions
Gave me:
at Settings::update(): &useSubstitutes = 0xb6e5c5cb
at RemoteStore::setOptions(): &useSubstitutes = 0xb6e5c5c7
That was not a fun one to debug!
70 lines
2 KiB
C++
70 lines
2 KiB
C++
#include "types.hh"
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#include <cstring>
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#include <cstddef>
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#include <cstdlib>
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#include <unistd.h>
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#include <signal.h>
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namespace nix {
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static void sigsegvHandler(int signo, siginfo_t * info, void * ctx)
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{
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/* Detect stack overflows by comparing the faulting address with
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the stack pointer. Unfortunately, getting the stack pointer is
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not portable. */
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bool haveSP = true;
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char * sp = 0;
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#if defined(__x86_64__) && defined(REG_RSP)
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sp = (char *) ((ucontext *) ctx)->uc_mcontext.gregs[REG_RSP];
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#elif defined(REG_ESP)
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sp = (char *) ((ucontext *) ctx)->uc_mcontext.gregs[REG_ESP];
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#else
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haveSP = false;
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#endif
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if (haveSP) {
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ptrdiff_t diff = (char *) info->si_addr - sp;
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if (diff < 0) diff = -diff;
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if (diff < 4096) {
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char msg[] = "error: stack overflow (possible infinite recursion)\n";
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[[gnu::unused]] int res = write(2, msg, strlen(msg));
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_exit(1); // maybe abort instead?
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}
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}
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/* Restore default behaviour (i.e. segfault and dump core). */
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struct sigaction act;
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sigfillset(&act.sa_mask);
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act.sa_handler = SIG_DFL;
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act.sa_flags = 0;
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if (sigaction(SIGSEGV, &act, 0)) abort();
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}
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void detectStackOverflow()
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{
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#if defined(SA_SIGINFO) && defined (SA_ONSTACK)
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/* Install a SIGSEGV handler to detect stack overflows. This
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requires an alternative stack, otherwise the signal cannot be
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delivered when we're out of stack space. */
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stack_t stack;
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stack.ss_size = 4096 * 4 + MINSIGSTKSZ;
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stack.ss_sp = new char[stack.ss_size];
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if (!stack.ss_sp) throw Error("cannot allocate alternative stack");
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stack.ss_flags = 0;
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if (sigaltstack(&stack, 0) == -1) throw SysError("cannot set alternative stack");
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struct sigaction act;
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sigfillset(&act.sa_mask);
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act.sa_sigaction = sigsegvHandler;
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act.sa_flags = SA_SIGINFO | SA_ONSTACK;
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if (sigaction(SIGSEGV, &act, 0))
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throw SysError("resetting SIGCHLD");
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#endif
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}
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}
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