Thanks for clarifying - I will look into what you have suggested. On Thu, 14 Feb 2019 at 20:16, Martin Sebor <msebor@xxxxxxxxx> wrote: > On 2/14/19 3:41 AM, Kalamatee wrote: > > ---------- Forwarded message --------- > > From: Kalamatee <kalamatee@xxxxxxxxx> > > Date: Thu, 14 Feb 2019 at 10:35 > > Subject: Re: format-truncation > > To: Jonathan Wakely <jwakely.gcc@xxxxxxxxx> > > > > > > > > > > On Thu, 14 Feb 2019 at 10:27, Kalamatee <kalamatee@xxxxxxxxx> wrote: > > > >> > >> > >> On Thu, 14 Feb 2019 at 10:19, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> > >> wrote: > >> > >>> On Thu, 14 Feb 2019 at 10:11, Kalamatee <kalamatee@xxxxxxxxx> wrote: > >>>> > >>>> Hello > >>>> > >>>> I am having trouble identifying how to fix the following error we > >>> encounter > >>>> when compiling AROS using our patched gcc 8.2. > >>>> > >>>> Compile failed: ccache > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/linux-x86_64/tools/crosstools/x86_64-aros-gcc > >>>> -iquote > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/components/utilities/ > >>>> -iquote /mnt/c/Users/kalam/AROS/svn-repo/AROS/arch/all-pc/acpica > >>> -iquote . > >>>> -mcmodel=large -mno-red-zone -mno-ms-bitfields -O2 > >>>> -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -Wall -Werror > >>>> -Wno-pointer-sign -Wno-parentheses -Wno-strict-aliasing > >>>> > >>> > -I/home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/AROS/Developer/include/acpica > >>>> -iquote > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/include > >>>> -iquote > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/include/platform > >>>> -DAROS_BUILD_TYPE=AROS_BUILD_TYPE_PERSONAL > >>>> > >>> > -I/home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/gen/arch/all-pc/acpica/acpica/include > >>>> -include > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/gen/arch/all-pc/acpica/acpica/include/acpica_deflibdefs.h > >>>> > >>> > -D__SRCFILENAME__="bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/components/utilities/utprint.c" > >>>> -c > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/components/utilities/utprint.c > >>>> -o > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/gen/arch/all-pc/acpica/acpica/utprint.o > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/components/utilities/utprint.c: > >>>> In function 'sprintf': > >>>> > >>> > /home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/Ports/acpica/acpica-unix-20190108/source/components/utilities/utprint.c:880:14: > >>>> error: specified bound 4294967295 exceeds 'INT_MAX' > >>>> [-Werror=format-truncation=] > >>>> Length = vsnprintf (String, ACPI_UINT32_MAX, Format, Args); > >>>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >>>> cc1: all warnings being treated as errors > >>>> mmakefile:918: recipe for target > >>>> > >>> > '/home/nick/builds/pc-x86_64-smp-gcc8/bin/pc-x86_64-smp/gen/arch/all-pc/acpica/acpica/utprint.o' > >>>> failed > >>>> > >>>> My problem is I cannot see where it is getting "INT_MAX" from as the > >>> bounds > >>>> for the 2nd parameter. > >>>> > >>>> The documentation for vsnprintf says "If the *maxlen* value is 0, no > >>>> characters are written, and *vsnprintf* returns 0. If the value is > >>> greater > >>>> than *INT_MAX* , then *vsnprintf* behaves identically to *vsprintf* in > >>> that > >>> > >>> Isn't that where it's coming from? > >>> > >>> The warning is telling you that the output could be unchecked, e.g. if > >>> it writes UINT32_MAX+1 then it would overflow your buffer. > >>> > >> > >> That's not what the warning/error is saying? It says ACPI_UNIT32_MAX > >> exceeds INT_MAX. It seems a bit misleading/confusing when it is valid > for > >> the second parameter to take values over INT_MAX. > >> > >> > > My point is - if it generated a warning/error for "UNIT32_MAX + 1" that > > _would_ be acceptable - but UNIT32_MAX itself is a constant and it can > see > > at compile time that can not over flow the buffer. > > snprintf (and vsnprintf) are required by POSIX to fail when the value > of n is greater than INT_MAX. Not all implementations conform to this > requirement, but calling snprintf with a size in excess of INT_MAX is > pointless even on implementations that don't fail because the function's > behavior is undefined if the amount of its output exceeds INT_MAX. When > there is no limit sprintf should be used instead. > > That said, the code you pointed to looks like an implementation of > sprintf (and vsnprintf). Unless that implementation conforms to C > and POSIX some instances of the warning will probably not make sense. > Not only that, the code GCC will emit may not make sense because it > assumes a conforming C implementation(*). So if that's the case > (i.e., if the implementation doesn't conform to C) you should prevent > GCC from assuming it does by -fno-builtin=snprintf. > > Martin > > [*] To be clear: the warning assumes POSIX conformance here. GCC > optimizations only assume C conformance. >
