/* * qemu user main * * Copyright (c) 2003 Fabrice Bellard * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include #include #include #include #include #include #include "qemu.h" #define DEBUG_LOGFILE "/tmp/qemu.log" #ifdef __APPLE__ #include # define environ (*_NSGetEnviron()) #endif static const char *interp_prefix = CONFIG_QEMU_PREFIX; #if defined(__i386__) && !defined(CONFIG_STATIC) /* Force usage of an ELF interpreter even if it is an ELF shared object ! */ const char interp[] __attribute__((section(".interp"))) = "/lib/ld-linux.so.2"; #endif /* for recent libc, we add these dummy symbols which are not declared when generating a linked object (bug in ld ?) */ #if (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3)) && !defined(CONFIG_STATIC) long __preinit_array_start[0]; long __preinit_array_end[0]; long __init_array_start[0]; long __init_array_end[0]; long __fini_array_start[0]; long __fini_array_end[0]; #endif /* XXX: on x86 MAP_GROWSDOWN only works if ESP <= address + 32, so we allocate a bigger stack. Need a better solution, for example by remapping the process stack directly at the right place */ unsigned long x86_stack_size = 512 * 1024; void gemu_log(const char *fmt, ...) { va_list ap; va_start(ap, fmt); vfprintf(stderr, fmt, ap); va_end(ap); } /* timers for rdtsc */ #if defined(__i386__) int64_t cpu_get_real_ticks(void) { int64_t val; asm volatile ("rdtsc" : "=A" (val)); return val; } #elif defined(__x86_64__) int64_t cpu_get_real_ticks(void) { uint32_t low,high; int64_t val; asm volatile("rdtsc" : "=a" (low), "=d" (high)); val = high; val <<= 32; val |= low; return val; } #else static uint64_t emu_time; int64_t cpu_get_real_ticks(void) { return emu_time++; } #endif #ifdef TARGET_I386 /***********************************************************/ /* CPUX86 core interface */ uint64_t cpu_get_tsc(CPUX86State *env) { return cpu_get_real_ticks(); } void cpu_loop() { } #endif void usage(void) { printf("qemu-" TARGET_ARCH " version " QEMU_VERSION ", Copyright (c) 2003-2004 Fabrice Bellard\n" "usage: qemu-" TARGET_ARCH " [-h] [-d opts] [-L path] [-s size] program [arguments...]\n" "Linux CPU emulator (compiled for %s emulation)\n" "\n" "-h print this help\n" "-L path set the elf interpreter prefix (default=%s)\n" "-s size set the stack size in bytes (default=%ld)\n" "\n" "debug options:\n" #ifdef USE_CODE_COPY "-no-code-copy disable code copy acceleration\n" #endif "-l options activate log (logfile=%s)\n" "-p xen port number\n", "-d xen domain id\n", TARGET_ARCH, interp_prefix, x86_stack_size, DEBUG_LOGFILE); _exit(1); } /* XXX: currently only used for async signals (see signal.c) */ CPUState *global_env; /* used only if single thread */ CPUState *cpu_single_env = NULL; /* used to free thread contexts */ TaskState *first_task_state; int main(int argc, char **argv) { const char *filename; struct target_pt_regs regs1, *regs = ®s1; struct image_info info1, *info = &info1; TaskState ts1, *ts = &ts1; CPUState *env; int optind; const char *r; if (argc <= 1) usage(); /* init debug */ cpu_set_log_filename(DEBUG_LOGFILE); cpu_set_log(0); optind = 1; for(;;) { if (optind >= argc) break; r = argv[optind]; if (r[0] != '-') break; optind++; r++; if (!strcmp(r, "-")) { break; } else if (!strcmp(r, "l")) { int mask; CPULogItem *item; if (optind >= argc) break; r = argv[optind++]; mask = cpu_str_to_log_mask(r); if (!mask) { printf("Log items (comma separated):\n"); for(item = cpu_log_items; item->mask != 0; item++) { printf("%-10s %s\n", item->name, item->help); } exit(1); } cpu_set_log(mask); } else if (!strcmp(r, "s")) { r = argv[optind++]; x86_stack_size = strtol(r, (char **)&r, 0); if (x86_stack_size <= 0) usage(); if (*r == 'M') x86_stack_size *= 1024 * 1024; else if (*r == 'k' || *r == 'K') x86_stack_size *= 1024; } else if (!strcmp(r, "L")) { interp_prefix = argv[optind++]; } else if (!strcmp(r, "p")) { qemu_host_page_size = atoi(argv[optind++]); if (qemu_host_page_size == 0 || (qemu_host_page_size & (qemu_host_page_size - 1)) != 0) { fprintf(stderr, "page size must be a power of two\n"); exit(1); } } else #ifdef USE_CODE_COPY if (!strcmp(r, "no-code-copy")) { code_copy_enabled = 0; } else #endif { usage(); } } if (optind >= argc) usage(); filename = argv[optind]; /* Zero out regs */ memset(regs, 0, sizeof(struct target_pt_regs)); /* Zero out image_info */ memset(info, 0, sizeof(struct image_info)); /* Scan interp_prefix dir for replacement files. */ init_paths(interp_prefix); /* NOTE: we need to init the CPU at this stage to get qemu_host_page_size */ env = cpu_init(); global_env = env; 
Chrono
======

When including the additional header file :file:`pybind11/chrono.h` conversions
from C++11 chrono datatypes to python datetime objects are automatically enabled.
This header also enables conversions of python floats (often from sources such
as ``time.monotonic()``, ``time.perf_counter()`` and ``time.process_time()``)
into durations.

An overview of clocks in C++11
------------------------------

A point of confusion when using these conversions is the differences between
clocks provided in C++11. There are three clock types defined by the C++11
standard and users can define their own if needed. Each of these clocks have
different properties and when converting to and from python will give different
results.

The first clock defined by the standard is ``std::chrono::system_clock``. This
clock measures the current date and time. However, this clock changes with to
updates to the operating system time. For example, if your time is synchronised
with a time server this clock will change. This makes this clock a poor choice
for timing purposes but good for measuring the wall time.

The second clock defined in the standard is ``std::chrono::steady_clock``.
This clock ticks at a steady rate and is never adjusted. This makes it excellent
for timing purposes, however the value in this clock does not correspond to the
current date and time. Often this clock will be the amount of time your system
has been on, although it does not have to be. This clock will never be the same
clock as the system clock as the system clock can change but steady clocks
cannot.

The third clock defined in the standard is ``std::chrono::high_resolution_clock``.
This clock is the clock that has the highest resolution out of the clocks in the
system. It is normally a typedef to either the system clock or the steady clock
but can be its own independent clock. This is important as when using these
conversions as the types you get in python for this clock might be different
depending on the system.
If it is a typedef of the system clock, python will get datetime objects, but if
it is a different clock they will be timedelta objects.

Provided conversions
--------------------

.. rubric:: C++ to Python

- ``std::chrono::system_clock::time_point`` → ``datetime.datetime``
    System clock times are converted to python datetime instances. They are
    in the local timezone, but do not have any timezone information attached
    to them (they are naive datetime objects).

- ``std::chrono::duration`` → ``datetime.timedelta``
    Durations are converted to timedeltas, any precision in the duration
    greater than microseconds is lost by rounding towards zero.

- ``std::chrono::[other_clocks]::time_point`` → ``datetime.timedelta``
    Any clock time that is not the system clock is converted to a time delta.
    This timedelta measures the time from the clocks epoch to now.

.. rubric:: Python to C++

- ``datetime.datetime`` or ``datetime.date`` or ``datetime.time`` → ``std::chrono::system_clock::time_point``
    Date/time objects are converted into system clock timepoints. Any
    timezone information is ignored and the type is treated as a naive
    object.

- ``datetime.timedelta`` → ``std::chrono::duration``
    Time delta are converted into durations with microsecond precision.

- ``datetime.timedelta`` → ``std::chrono::[other_clocks]::time_point``
    Time deltas that are converted into clock timepoints are treated as
    the amount of time from the start of the clocks epoch.

- ``float`` → ``std::chrono::duration``
    Floats that are passed to C++ as durations be interpreted as a number of
    seconds. These will be converted to the duration using ``duration_cast``
    from the float.

- ``float`` → ``std::chrono::[other_clocks]::time_point``
    Floats that are passed to C++ as time points will be interpreted as the
    number of seconds from the start of the clocks epoch.
generated by cgit v1.2.3 (git 2.25.1) at 2026-01-06 21:27:25 +0000