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diff --git a/share/doc/gccint/Stack-Checking.html b/share/doc/gccint/Stack-Checking.html new file mode 100644 index 0000000..1ce4943 --- /dev/null +++ b/share/doc/gccint/Stack-Checking.html @@ -0,0 +1,205 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). 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GCC will not do +other special processing. + +</li><li> If <code>STACK_CHECK_BUILTIN</code> is zero and the value of the +<code>STACK_CHECK_STATIC_BUILTIN</code> macro is nonzero, GCC will assume +that you have arranged for static stack checking (checking of the +static stack frame of functions) to be done at appropriate places +in the configuration files. GCC will only emit code to do dynamic +stack checking (checking on dynamic stack allocations) using the third +approach below. + +</li><li> If neither of the above are true, GCC will generate code to periodically +“probe” the stack pointer using the values of the macros defined below. +</li></ol> + +<p>If neither STACK_CHECK_BUILTIN nor STACK_CHECK_STATIC_BUILTIN is defined, +GCC will change its allocation strategy for large objects if the option +<samp>-fstack-check</samp> is specified: they will always be allocated +dynamically if their size exceeds <code>STACK_CHECK_MAX_VAR_SIZE</code> bytes. +</p> +<dl> +<dt><a name="index-STACK_005fCHECK_005fBUILTIN"></a>Macro: <strong>STACK_CHECK_BUILTIN</strong></dt> +<dd><p>A nonzero value if stack checking is done by the configuration files in a +machine-dependent manner. You should define this macro if stack checking +is required by the ABI of your machine or if you would like to do stack +checking in some more efficient way than the generic approach. The default +value of this macro is zero. +</p></dd></dl> + +<dl> +<dt><a name="index-STACK_005fCHECK_005fSTATIC_005fBUILTIN"></a>Macro: <strong>STACK_CHECK_STATIC_BUILTIN</strong></dt> +<dd><p>A nonzero value if static stack checking is done by the configuration files +in a machine-dependent manner. You should define this macro if you would +like to do static stack checking in some more efficient way than the generic +approach. The default value of this macro is zero. +</p></dd></dl> + +<dl> +<dt><a name="index-STACK_005fCHECK_005fPROBE_005fINTERVAL_005fEXP"></a>Macro: <strong>STACK_CHECK_PROBE_INTERVAL_EXP</strong></dt> +<dd><p>An integer specifying the interval at which GCC must generate stack probe +instructions, defined as 2 raised to this integer. You will normally +define this macro so that the interval be no larger than the size of +the “guard pages” at the end of a stack area. The default value +of 12 (4096-byte interval) is suitable for most systems. +</p></dd></dl> + +<dl> +<dt><a name="index-STACK_005fCHECK_005fMOVING_005fSP"></a>Macro: <strong>STACK_CHECK_MOVING_SP</strong></dt> +<dd><p>An integer which is nonzero if GCC should move the stack pointer page by page +when doing probes. This can be necessary on systems where the stack pointer +contains the bottom address of the memory area accessible to the executing +thread at any point in time. In this situation an alternate signal stack +is required in order to be able to recover from a stack overflow. The +default value of this macro is zero. +</p></dd></dl> + +<dl> +<dt><a name="index-STACK_005fCHECK_005fPROTECT"></a>Macro: <strong>STACK_CHECK_PROTECT</strong></dt> +<dd><p>The number of bytes of stack needed to recover from a stack overflow, for +languages where such a recovery is supported. The default value of 4KB/8KB +with the <code>setjmp</code>/<code>longjmp</code>-based exception handling mechanism and +8KB/12KB with other exception handling mechanisms should be adequate for most +architectures and operating systems. +</p></dd></dl> + +<p>The following macros are relevant only if neither STACK_CHECK_BUILTIN +nor STACK_CHECK_STATIC_BUILTIN is defined; you can omit them altogether +in the opposite case. +</p> +<dl> +<dt><a name="index-STACK_005fCHECK_005fMAX_005fFRAME_005fSIZE"></a>Macro: <strong>STACK_CHECK_MAX_FRAME_SIZE</strong></dt> +<dd><p>The maximum size of a stack frame, in bytes. GCC will generate probe +instructions in non-leaf functions to ensure at least this many bytes of +stack are available. If a stack frame is larger than this size, stack +checking will not be reliable and GCC will issue a warning. The +default is chosen so that GCC only generates one instruction on most +systems. You should normally not change the default value of this macro. +</p></dd></dl> + +<dl> +<dt><a name="index-STACK_005fCHECK_005fFIXED_005fFRAME_005fSIZE"></a>Macro: <strong>STACK_CHECK_FIXED_FRAME_SIZE</strong></dt> +<dd><p>GCC uses this value to generate the above warning message. It +represents the amount of fixed frame used by a function, not including +space for any callee-saved registers, temporaries and user variables. +You need only specify an upper bound for this amount and will normally +use the default of four words. +</p></dd></dl> + +<dl> +<dt><a name="index-STACK_005fCHECK_005fMAX_005fVAR_005fSIZE"></a>Macro: <strong>STACK_CHECK_MAX_VAR_SIZE</strong></dt> +<dd><p>The maximum size, in bytes, of an object that GCC will place in the +fixed area of the stack frame when the user specifies +<samp>-fstack-check</samp>. +GCC computed the default from the values of the above macros and you will +normally not need to override that default. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fSTACK_005fCLASH_005fPROTECTION_005fALLOCA_005fPROBE_005fRANGE"></a>Target Hook: <em>HOST_WIDE_INT</em> <strong>TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE</strong> <em>(void)</em></dt> +<dd><p>Some targets have an ABI defined interval for which no probing needs to be done. +When a probe does need to be done this same interval is used as the probe distance +up when doing stack clash protection for alloca. +On such targets this value can be set to override the default probing up interval. +Define this variable to return nonzero if such a probe range is required or zero otherwise. +Defining this hook also requires your functions which make use of alloca to have at least 8 byes +of outgoing arguments. If this is not the case the stack will be corrupted. +You need not define this macro if it would always have the value zero. +</p></dd></dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Frame-Registers.html#Frame-Registers" accesskey="n" rel="next">Frame Registers</a>, Previous: <a href="Exception-Handling.html#Exception-Handling" accesskey="p" rel="previous">Exception Handling</a>, Up: <a href="Stack-and-Calling.html#Stack-and-Calling" accesskey="u" rel="up">Stack and Calling</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |