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理想的方法契约：
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方法功能描述
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参数定义及合法性要求
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调用线程环境要求
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返回值定义
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当参数不合法时，方法的行为
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当出现其他错误时，方法的行为
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当方法正常返回时，相关对象(系统)的状态
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当方法抛出异常时，相关对象(系统)的状态
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其中最后一条即所谓的“异常安全”
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异常或错误，追究其原因，有三种:
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程序逻辑错误
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非法的用户输入
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硬件错误
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其中非法的用户输入其实是可以(或者应该)不用异常或错误进行处理的，属于程序正常的流程
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因为Java或者任何支持try catch的异常系统，建立异常对象通常会收集调用栈信息，是比较昂贵的路径，
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除非出错否则你是不想创建异常的。但是在实际实践中，为了系统设计上的“干净”和开发的方便，
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对非法用户输入的处理常常也用异常系统进行了统一处理。这算是开发维护成本和运行效率的取舍吧
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程序逻辑错误，在运维系统越来越先进的今天，很多团队选择比较激进的let it fail哲学，
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辅以充分的单元和集成测试，在大部分商业应用场景都是可行的。表现在代码里，就是任其崩溃，
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语言运行环境或应用框架内建的最后一层捕获机制会去处理异常。这个过程虽然不需要程序员做什么，
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但是有经验的老司机还是会去考虑一些敏感场景的异常安全问题，
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比如影响到持久化数据正确性或者与其他系统交互正确性的场景。
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硬件错误通常是不做考虑的，那完全是架构需要操心的事。
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Design by Contract (契约式设计)
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契约式设计强调三个概念：前置条件，后置条件和不变式
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错误处理
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程序本身的组成形式都能展开成一条条最基本的语句，这个东西会读取输入，中间各种运算，产生输出。
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我们使用输入输出的时候已经天然带类型了，自带一层约束
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我们整个流程是有预期的，从输入到输出，中间的各种阶段都会有预期。
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天然类型的约束可能不符合我们对输入输出的预期，所以更健壮的代码可以对输入输出进行检查。加入更多的约束
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程序有依赖硬件，如果硬件出错，那么不符合预期是无法从程序层面解决的。这是无需处理
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如果输入符合预期，输出不符合预期，那可能就是程序逻辑错误
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如果输入不符合预期，那么可能就是
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当如输入输出可以广泛一点的定义，也包括线程环境，数据状态等各种信息
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问题在于如何处理，我理解的处理是分环境的，开发环境下的处理方式，和生产时的处理方式不一定一样，开发要直接崩溃
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打印调用栈，生产时要看是什么程序，如果时系统级程序也要直接崩溃，或者时数据库要弄事务，如果是后端这种，可能就打日志
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然后处理掉
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那么基于此，在c++如何处理
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那一定是基于宏判断是Debug还是release 然后下面细分类型，也可以像spdlog一样有日志级别
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那么问题来了 如果是不重要的情景下如何不让他崩溃，对我的程序来说解码不符合预期应当忽略整个报文的结果
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或者激进一点 只忽略这一个报文的一个字段的结果
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那么返回值应该如何处理加std::optional？
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我认为std::optional 其实很局限 他就表达了空对象概念，当然我可以全局弄个错误码，但是那不就是c的方式了吗
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他本质就是c的方式的语法糖
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错误处理就c的方式错误码方式，异常，然后就是let it fail 直接崩， 然后各种事物，乱七八糟根据具体情况来的
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总体来看像是后端那种程序我直接打日志的错误不敏感的，异常要好的多
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那我现在开始定义了
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(lldb) settings list
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Top level variables:
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auto-confirm -- If true all confirmation prompts will receive their default reply.
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disassembly-format -- The default disassembly format string to use when disassembling instruction sequences.
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frame-format -- The default frame format string to use when displaying stack frame information for
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threads.
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notify-void -- Notify the user explicitly if an expression returns void (default: false).
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prompt -- The debugger command line prompt displayed for the user.
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script-lang -- The script language to be used for evaluating user-written scripts.
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stop-disassembly-count -- The number of disassembly lines to show when displaying a stopped context.
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stop-disassembly-display -- Control when to display disassembly when displaying a stopped context.
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stop-line-count-after -- The number of sources lines to display that come after the current source line when
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displaying a stopped context.
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stop-line-count-before -- The number of sources lines to display that come before the current source line when
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displaying a stopped context.
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highlight-source -- If true, LLDB will highlight the displayed source code.
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stop-show-column -- If true, LLDB will use the column information from the debug info to mark the current
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position when displaying a stopped context.
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stop-show-column-ansi-prefix -- When displaying the column marker in a color-enabled (i.e. ANSI) terminal, use the
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ANSI terminal code specified in this format at the immediately before the column to
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be marked.
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stop-show-column-ansi-suffix -- When displaying the column marker in a color-enabled (i.e. ANSI) terminal, use the
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ANSI terminal code specified in this format immediately after the column to be marked.
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term-width -- The maximum number of columns to use for displaying text.
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thread-format -- The default thread format string to use when displaying thread information.
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thread-stop-format -- The default thread format string to use when displaying thread information as part
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of the stop display.
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use-external-editor -- Whether to use an external editor or not.
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use-color -- Whether to use Ansi color codes or not.
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auto-one-line-summaries -- If true, LLDB will automatically display small structs in one-liner format (default:
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true).
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auto-indent -- If true, LLDB will auto indent/outdent code. Currently only supported in the REPL
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(default: true).
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print-decls -- If true, LLDB will print the values of variables declared in an expression. Currently
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only supported in the REPL (default: true).
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tab-size -- The tab size to use when indenting code in multi-line input mode (default: 4).
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escape-non-printables -- If true, LLDB will automatically escape non-printable and escape characters when
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formatting strings.
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frame-format-unique -- The default frame format string to use when displaying stack frameinformation for
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threads from thread backtrace unique.
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'target' variables:
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default-arch -- Default architecture to choose, when there's a choice.
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move-to-nearest-code -- Move breakpoints to nearest code.
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language -- The language to use when interpreting expressions entered in commands.
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expr-prefix -- Path to a file containing expressions to be prepended to all expressions.
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prefer-dynamic-value -- Should printed values be shown as their dynamic value.
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enable-synthetic-value -- Should synthetic values be used by default whenever available.
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skip-prologue -- Skip function prologues when setting breakpoints by name.
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breakpoint-smart-move -- Check function boundaries when setting breakpoints by file and line.
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source-map -- Source path remappings are used to track the change of location between a
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source file when built, and where it exists on the current system. It
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consists of an array of duples, the first element of each duple is some part
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(starting at the root) of the path to the file when it was built, and the
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second is where the remainder of the original build hierarchy is rooted on the
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local system. Each element of the array is checked in order and the first one
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that results in a match wins.
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exec-search-paths -- Executable search paths to use when locating executable files whose paths
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don't match the local file system.
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debug-file-search-paths -- List of directories to be searched when locating debug symbol files. See also
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symbols.enable-external-lookup.
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clang-module-search-paths -- List of directories to be searched when locating modules for Clang.
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auto-import-clang-modules -- Automatically load Clang modules referred to by the program.
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import-std-module -- Import the C++ std module to improve debugging STL containers.
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auto-apply-fixits -- Automatically apply fix-it hints to expressions.
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notify-about-fixits -- Print the fixed expression text.
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save-jit-objects -- Save intermediate object files generated by the LLVM JIT
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max-children-count -- Maximum number of children to expand in any level of depth.
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max-string-summary-length -- Maximum number of characters to show when using %s in summary strings.
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max-memory-read-size -- Maximum number of bytes that 'memory read' will fetch before --force must be
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specified.
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breakpoints-use-platform-avoid-list -- Consult the platform module avoid list when setting non-module specific
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breakpoints.
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arg0 -- The first argument passed to the program in the argument array which can be
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different from the executable itself.
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run-args -- A list containing all the arguments to be passed to the executable when it is
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run. Note that this does NOT include the argv[0] which is in target.arg0.
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env-vars -- A list of all the environment variables to be passed to the executable's
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environment, and their values.
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inherit-env -- Inherit the environment from the process that is running LLDB.
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input-path -- The file/path to be used by the executable program for reading its standard
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input.
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output-path -- The file/path to be used by the executable program for writing its standard
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output.
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error-path -- The file/path to be used by the executable program for writing its standard
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error.
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detach-on-error -- debugserver will detach (rather than killing) a process if it loses connection
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with lldb.
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preload-symbols -- Enable loading of symbol tables before they are needed.
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disable-aslr -- Disable Address Space Layout Randomization (ASLR)
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disable-stdio -- Disable stdin/stdout for process (e.g. for a GUI application)
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inline-breakpoint-strategy -- The strategy to use when settings breakpoints by file and line. Breakpoint
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locations can end up being inlined by the compiler, so that a compile unit
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'a.c' might contain an inlined function from another source file. Usually this
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is limited to breakpoint locations from inlined functions from header or other
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include files, or more accurately non-implementation source files. Sometimes
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code might #include implementation files and cause inlined breakpoint
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locations in inlined implementation files. Always checking for inlined
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breakpoint locations can be expensive (memory and time), so if you have a
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project with many headers and find that setting breakpoints is slow, then you
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can change this setting to headers. This setting allows you to control exactly
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which strategy is used when setting file and line breakpoints.
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x86-disassembly-flavor -- The default disassembly flavor to use for x86 or x86-64 targets.
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use-hex-immediates -- Show immediates in disassembly as hexadecimal.
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hex-immediate-style -- Which style to use for printing hexadecimal disassembly values.
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use-fast-stepping -- Use a fast stepping algorithm based on running from branch to branch rather
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than instruction single-stepping.
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load-script-from-symbol-file -- Allow LLDB to load scripting resources embedded in symbol files when available.
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load-cwd-lldbinit -- Allow LLDB to .lldbinit files from the current directory automatically.
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memory-module-load-level -- Loading modules from memory can be slow as reading the symbol tables and other
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data can take a long time depending on your connection to the debug target.
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This setting helps users control how much information gets loaded when loading
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modules from memory.'complete' is the default value for this setting which
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will load all sections and symbols by reading them from memory (slowest, most
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accurate). 'partial' will load sections and attempt to find function bounds
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without downloading the symbol table (faster, still accurate, missing symbol
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names). 'minimal' is the fastest setting and will load section data with no
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symbols, but should rarely be used as stack frames in these memory regions
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will be inaccurate and not provide any context (fastest).
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display-expression-in-crashlogs -- Expressions that crash will show up in crash logs if the host system supports
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executable specific crash log strings and this setting is set to true.
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trap-handler-names -- A list of trap handler function names, e.g. a common Unix user process one is
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_sigtramp.
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display-runtime-support-values -- If true, LLDB will show variables that are meant to support the operation of a
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language's runtime support.
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display-recognized-arguments -- Show recognized arguments in variable listings by default.
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non-stop-mode -- Disable lock-step debugging, instead control threads independently.
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require-hardware-breakpoint -- Require all breakpoints to be hardware breakpoints.
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'target.experimental' variables:
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inject-local-vars -- If true, inject local variables explicitly into the expression text. This will
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fix symbol resolution when there are name collisions between ivars and local
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variables. But it can make expressions run much more slowly.
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use-modern-type-lookup -- If true, use Clang's modern type lookup infrastructure.
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cache-evaluating-expressions -- If true, evaluated expressions ast is cached for further use.
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cache-evaluating-expressions-limit -- Expression ast cache limit.
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'target.process' variables:
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disable-memory-cache -- Disable reading and caching of memory in fixed-size units.
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extra-startup-command -- A list containing extra commands understood by the particular process plugin
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used. For instance, to turn on debugserver logging set this to
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"QSetLogging:bitmask=LOG_DEFAULT;"
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ignore-breakpoints-in-expressions -- If true, breakpoints will be ignored during expression evaluation.
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unwind-on-error-in-expressions -- If true, errors in expression evaluation will unwind the stack back to the state
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before the call.
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python-os-plugin-path -- A path to a python OS plug-in module file that contains a OperatingSystemPlugIn
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class.
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stop-on-sharedlibrary-events -- If true, stop when a shared library is loaded or unloaded.
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detach-keeps-stopped -- If true, detach will attempt to keep the process stopped.
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memory-cache-line-size -- The memory cache line size
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optimization-warnings -- If true, warn when stopped in code that is optimized where stepping and variable
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availability may not behave as expected.
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stop-on-exec -- If true, stop when a shared library is loaded or unloaded.
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utility-expression-timeout -- The time in seconds to wait for LLDB-internal utility expressions.
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'target.process.thread' variables:
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step-in-avoid-nodebug -- If true, step-in will not stop in functions with no debug information.
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step-out-avoid-nodebug -- If true, when step-in/step-out/step-over leave the current frame, they will continue to
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step out till they come to a function with debug information. Passing a frame argument to
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step-out will override this option.
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step-avoid-regexp -- A regular expression defining functions step-in won't stop in.
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step-avoid-libraries -- A list of libraries that source stepping won't stop in.
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trace-thread -- If true, this thread will single-step and log execution.
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max-backtrace-depth -- Maximum number of frames to backtrace.
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'platform' variables:
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use-module-cache -- Use module cache.
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module-cache-directory -- Root directory for cached modules.
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'symbols' variables:
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enable-external-lookup -- Control the use of external tools and repositories to locate symbol files. Directories
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listed in target.debug-file-search-paths and directory of the executable are always
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checked first for separate debug info files. Then depending on this setting: On macOS,
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Spotlight would be also used to locate a matching .dSYM bundle based on the UUID of the
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executable. On NetBSD, directory /usr/libdata/debug would be also searched. On platforms
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other than NetBSD directory /usr/lib/debug would be also searched.
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clang-modules-cache-path -- The path to the clang modules cache directory (-fmodules-cache-path).
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'interpreter' variables:
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expand-regex-aliases -- If true, regular expression alias commands will show the expanded command that will
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be executed. This can be used to debug new regular expression alias commands.
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prompt-on-quit -- If true, LLDB will prompt you before quitting if there are any live processes being
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debugged. If false, LLDB will quit without asking in any case.
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stop-command-source-on-error -- If true, LLDB will stop running a 'command source' script upon encountering an error.
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space-repl-prompts -- If true, blank lines will be printed between between REPL submissions.
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echo-commands -- If true, commands will be echoed before they are evaluated.
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echo-comment-commands -- If true, commands will be echoed even if they are pure comment lines.
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'plugin' variables:
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'plugin.jit-loader' variables:
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'plugin.jit-loader.gdb' variables:
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enable -- Enable GDB's JIT compilation interface (default: enabled on all platforms except macOS)
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'plugin.process' variables:
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'plugin.process.windows' variables:
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suppress-debug-output -- If true, debug output string events will be suppressed
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'plugin.process.gdb-remote' variables:
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packet-timeout -- Specify the default packet timeout in seconds.
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target-definition-file -- The file that provides the description for remote target registers.
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use-libraries-svr4 -- If true, the libraries-svr4 feature will be used to get a hold of the process's loaded
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modules.
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'plugin.symbol-file' variables:
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'plugin.symbol-file.dwarf' variables:
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comp-dir-symlink-paths -- If the DW_AT_comp_dir matches any of these paths the symbolic links will be resolved at
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DWARF parse time.
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ignore-file-indexes -- Ignore indexes present in the object files and always index DWARF manually.
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'plugin.structured-data' variables:
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'plugin.structured-data.darwin-log' variables:
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enable-on-startup -- Enable Darwin os_log collection when debugged process is launched or attached.
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auto-enable-options -- Specify the options to 'plugin structured-data darwin-log enable' that should be applied when
|
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automatically enabling logging on startup/attach.
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||||
(lldb)
|
||||
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