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diff --git a/static/openbsd/man1/gcc-local.1 b/static/openbsd/man1/gcc-local.1 new file mode 100644 index 00000000..e9fad577 --- /dev/null +++ b/static/openbsd/man1/gcc-local.1 @@ -0,0 +1,408 @@ +.\" $OpenBSD: gcc-local.1,v 1.59 2025/11/18 11:13:22 miod Exp $ +.\" +.\" Copyright (c) 2002 Marc Espie +.\" Copyright (c) 2003 Anil Madhavapeddy +.\" +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.Dd $Mdocdate: November 18 2025 $ +.Dt GCC-LOCAL 1 +.Os +.Sh NAME +.Nm gcc-local +.Nd local modifications to gcc +.Sh DESCRIPTION +.Ox +uses derivatives of +.Xr gcc 1 +version 4.2.1. +The software comes with specific modifications for +.Ox : +.Bl -dash +.It +For the C programming language, +.Nm gcc +defaults to the +.Em gnu99 +standard, +not +.Em gnu89 . +The +.Fl std +option can be used to select a different language standard. +.It +.Nm gcc +does not search under +.Pa /usr/local +for include files nor for libraries: +as a system compiler, it only searches the system paths by default. +.It +On all architectures where the stack is non-executable, +trampoline code marks the smallest possible area around the trampoline stub +executable using +.Xr mprotect 2 . +.It +Trampoline code generation is disabled by default. +Code requiring trampolines will not compile without +.Fl ftrampolines . +The warning flag +.Fl Wtrampolines +can be used to locate trampoline instances if trampoline generation +is re-enabled. +.It +The +.Fl O2 +option does not include +.Fl fstrict-aliasing , +as this option causes issues on some legacy code. +.Fl fstrict-aliasing +is very unsafe with code that plays tricks with casts, bypassing the +already weak type system of C. +.It +The +.Fl O2 +option does not include +.Fl fstrict-overflow , +as this option causes issues on some legacy code. +.Fl fstrict-overflow +can cause surprising optimizations to occur, possibly deleting security +critical overflow checks. +.It +The +.Fl O2 +option does not include the +.Fl ftree-vrp +optimization as it is known to be broken. +.It +.Nm gcc +recognizes the extra format attribute syslog, to better match +the definition of +.Xr syslog 3 , +and silence erroneous warnings when used with +.Fl pedantic . +.It +.Nm gcc +recognizes the attribute +.Cm __nonnull__ , +which can be used to mark arguments that can't be +.Dv NULL . +The printf format attribute does not imply +.Cm __nonnull__ +for the format. +This allows for correct format checking on the +.Xr err 3 +function family. +.It +.Nm gcc +recognizes the extra attribute +.Cm __sentinel__ , +which can be used to mark varargs function that need a +.Dv NULL +pointer to mark argument termination, like +.Xr execl 3 . +This exposes latent bugs for 64-bit architectures, +where a terminating 0 will expand to a 32-bit int, and not a full-fledged +64-bits pointer. +.It +On alpha, +.Fl mieee +is enabled by default to enable full compliance with +the IEEE floating point standard, +although the +.Dq inexact +flag is not maintained. +Additionally, rounding mode is dynamic. +.It +.Nm gcc +comes with the +.Dq ProPolice +stack protection extension, which is enabled by default. +This extension reorders local variable declarations and adds stack consistency +checks at runtime, in order to detect stack overflows, and will attempt to +report the problem in the system logs by calling +.Xr syslog 3 +with a +.Dv LOG_CRIT +priority message: +.Dq stack overflow in function XXX , +and abort the faulting process. +It can be turned off using the +.Fl fno-stack-protector +command line option. +Note that the stack protector relies on some support code in libc. +Stand-alone programs not linked against libc must either provide their own +support bits or use the +.Fl fno-stack-protector +option. +.Pp +There is a +.Fl fstack-protector-all +option that turns stack protection code on for all functions +and disables any heuristic that flags some functions as safe. +This extended checking has a moderate runtime cost though. +There is a +.Fl fstack-protector-strong +option, similar to +.Fl fstack-protector , +which includes additional functions to be protected \(em those that +have local array definitions +or have references to local frame addresses. +.It +On amd64, +.Fl msave-args +can be passed to the compiler to have functions save their register +arguments on the stack, while maintaining compatibility with the +System 5 AMD64 ABI. +This enables tools and debuggers that understand this semantic to +trivially generate stack traces that include function arguments. +.It +On all architectures, +.Nm gcc +generates position-independent executables +.Pq PIEs +by default, allowing the system to load the resulting binary +at a random location. +This behavior can be turned off by passing +.Fl fno-pie +to the compiler and +.Fl nopie +to the linker. +.It +.Nm gcc +recognizes a new flag which is enabled by default, +.Fl Wbounded , +to perform basic checks on functions which accept buffers and sizes. +An extra attribute, +.Cm __bounded__ , +has been added to mark functions that can be +checked this way. +.It +.Nm gcc +recognizes a new format attribute, kprintf, to deal with the extra format +arguments +.Ql %b , +.Ql %r , +and +.Ql %z +used in the +.Ox +kernel. +.It +.Nm gcc +does not store its version string in objects. +This behavior can be restored with +.Fl fident . +.It +The option +.Fl fstack-shuffle +will randomize the order of stack variables at compile time, +which can be helpful to find bugs. +.It +.Nm gcc +will not move variables initialized with the value zero +from the data section to the bss section. +The default behaviour of +.Nm gcc +on other systems is to perform this action, which can be restored for +.Ox +with +.Fl fzero-initialized-in-bss . +.It +.Nm gcc +does not warn for cast expressions used as lvalues outside of +.Fl pedantic . +.It +.Nm gcc +does not warn for passing pointer arguments or assignment with +different signedness outside of +.Fl pedantic . +This can be +re-enabled with the +.Fl Wpointer-sign +flag. +.It +.Nm gcc +recognizes the preprocessor flag +.Fl CC +that lets comments in macros pass through to the output (except in +.Fl traditional +mode). +.It +The warning option +.Fl Wsystem-headers , +which makes +.Nm gcc +report warnings in systems headers, +is enabled by default. +.It +.Nm gcc +supports two extra warning options: +.Bl -item +.It +.Fl Wframe-larger-than= Ns Va N +.Po +and its non-portable alias +.Fl Wstack-larger-than- Ns Va N +.Pc +will report functions using more than +.Va N +bytes of stack space for their local variables. +Stack space used for other purposes (such as register window saving, +callee-saved registers, or outbound arguments storage) +is not taken into account for this check. +.It +.Fl Wvariable-decl +will report automatic variable declarations whose size cannot be +determined at compile-time. +.El +.It +.Nm gcc +has backported support for the GCC binary integer constants extension, +which was first introduced in +.Nm gcc 4.3 . +.It +The behavior of +.Fl Wshadow +in +.Nm gcc +has been altered to behave similarly to +.Nm gcc 4.8 +and not warn about variables or parameters that shadow a global +function unless the variable or parameter is of type pointer-to-function. +.El +.Sh ATTRIBUTES +The +.Cm __bounded__ +attribute is used to type-check functions whose parameters pass fixed-length +buffers and their sizes. +The syntax for normal buffers is: +.Pp +.Ic __attribute__ Ns Po Po +.Cm __bounded__ Ns Pq Cm __buffer__ , Va buffer , length +.Pc Pc +.Pp +where +.Fa buffer +contains the parameter number (starting from 1) of the pointer to the buffer, +and +.Fa length +contains the parameter number of the buffer length argument. +.Pp +.Nm gcc +will emit a warning if the length argument is a constant larger than the +actual size of the buffer. +If the buffer is not a statically declared array of fixed length, no warnings +will be generated. +Refer to +.Xr memcpy 3 +for an example of a function with this check. +.Pp +For checking strings, just use +.Cm __string__ +instead of +.Cm __buffer__ : +.Pp +.Ic __attribute__ Ns Po Po +.Cm __bounded__ Ns Pq Cm __string__ , Va buffer , length +.Pc Pc +.Pp +In addition to the checks described above, this also tests if the +.Va length +argument was wrongly derived from a +.Fn sizeof "void *" +operation. +.Xr strlcpy 3 +is a good example of a string function with this check. +.Pp +If a function needs string checking like +.Cm __string__ +but operates on element counts rather than buffer sizes, use +.Cm __wcstring__ : +.Pp +.Ic __attribute__ Ns Po Po +.Cm __bounded__ Ns Pq Cm __wcstring__ , Va buffer , count +.Pc Pc +.Pp +An example of a string function with this check is +.Xr wcslcpy 3 . +.Pp +Some functions specify the length as two arguments: +the number of elements and the size of each element. +In this case, use the +.Cm __size__ +attribute: +.Pp +.Ic __attribute__ Ns Po Po +.Cm __bounded__ Ns Pq Cm __size__ , Va buffer , nmemb , size +.Pc Pc +.Pp +where +.Va buffer +contains the parameter number of the pointer to the buffer, +.Va nmemb +contains the parameter number of the number of members, and +.Va size +has the parameter number of the size of each element. +The type checks performed by +.Cm __size__ +are the same as the +.Cm __buffer__ +attribute. +See +.Xr fread 3 +for an example of this type of function. +.Pp +If a function accepts a buffer parameter and specifies that it has to be of a +minimum length, the __minbytes__ attribute can be used: +.Pp +.Ic __attribute__ Ns Po Po +.Cm __bounded__ Ns Pq Cm __minbytes__ , Va buffer , minsize +.Pc Pc +.Pp +where +.Va buffer +contains the parameter number of the pointer to the buffer, and +.Va minsize +specifies the minimum number of bytes that the buffer should be. +.Xr ctime_r 3 +is an example of this type of function. +.Pp +If +.Fl Wbounded +is specified with +.Fl Wformat , +additional checks are performed on +.Xr sscanf 3 +format strings. +The +.Ql %s +fields are checked for incorrect bound lengths by checking the size of the +buffer associated with the format argument. +.Sh SEE ALSO +.Xr gcc 1 +.Sh CAVEATS +The +.Fl Wbounded +flag only works with statically allocated fixed-size buffers. +Since it is applied at compile-time, dynamically allocated memory buffers +and non-constant arguments are ignored. |