| Message ID | 1419373336-17800-3-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | New |
| Headers | show |
Am 23.12.2014 um 23:22 schrieb Peter Maydell: > The mingw32 compiler complains about trying to print variables of type > ssize_t with the %z format string specifier. Since we're printing it > as unsigned hex anyway, cast to size_t to silence the warning. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > I suspect that this is a compiler bug, but this is the only instance > in the codebase so I'm prepared to work around it to get to a point > where we can turn on warnings-as-errors for w32, because some of the > w32-specific errors really are flagging up issues we need to fix. > --- > hw/ppc/spapr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 08401e0..9aaa800 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1438,7 +1438,7 @@ static void ppc_spapr_init(MachineState *machine) > } > if (spapr->rtas_size > RTAS_MAX_SIZE) { > hw_error("RTAS too big ! 0x%zx bytes (max is 0x%x)\n", > - spapr->rtas_size, RTAS_MAX_SIZE); > + (size_t)spapr->rtas_size, RTAS_MAX_SIZE); > exit(1); > } > g_free(filename); Which compiler did you use? I get no warning with Debian's x86_64-w64-mingw32-gcc 4.6.3 or native MinGW-w32 compilers. Stefan
On 23 December 2014 at 22:36, Stefan Weil <sw@weilnetz.de> wrote: > Am 23.12.2014 um 23:22 schrieb Peter Maydell: >> --- a/hw/ppc/spapr.c >> +++ b/hw/ppc/spapr.c >> @@ -1438,7 +1438,7 @@ static void ppc_spapr_init(MachineState *machine) >> } >> if (spapr->rtas_size > RTAS_MAX_SIZE) { >> hw_error("RTAS too big ! 0x%zx bytes (max is 0x%x)\n", >> - spapr->rtas_size, RTAS_MAX_SIZE); >> + (size_t)spapr->rtas_size, RTAS_MAX_SIZE); >> exit(1); >> } >> g_free(filename); > > > Which compiler did you use? I get no warning with Debian's > x86_64-w64-mingw32-gcc 4.6.3 or > native MinGW-w32 compilers. $ i586-mingw32msvc-gcc --version i586-mingw32msvc-gcc (GCC) 4.2.1-sjlj (mingw32-2) Yes, this is ancient... it's from the Debian mingw32 package. I just use this for compile testing, not for trying to run. I should probably switch to the w64 compiler for build tests; I forget now if there was a reason why I hadn't. I suspect, as I say, that this is just a generic old-gcc bug, but it's the only one in the codebase, so it seems easiest just to fix it. -- PMM
On 12/23/2014 03:22 PM, Peter Maydell wrote: > The mingw32 compiler complains about trying to print variables of type > ssize_t with the %z format string specifier. Since we're printing it > as unsigned hex anyway, cast to size_t to silence the warning. Hmm. I wonder if mingw headers are mixing 'long' and 'unsigned int' (or maybe 'unsigned long' and 'int') for the underlying definitions of 'ssize_t' vs. 'size_t'; both are 32-bits on the platform, but a difference in underlying type would definitely explain why you get a compiler warning if you use %zd with size_t or %zu with ssize_t. On the other hand, the warning I've most often seen is that native windows completely lacks %z support, so gcc is smart enough to warn that ANY use of %z is not going to work, for a function marked __attribute__((__printf__)) on mingw. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > I suspect that this is a compiler bug, but this is the only instance > in the codebase so I'm prepared to work around it to get to a point > where we can turn on warnings-as-errors for w32, because some of the > w32-specific errors really are flagging up issues we need to fix. With new enough mingw headers, the alternative solution is to guarantee that #__USE_MINGW_ANSI_STDIO is defined before including standard headers, then %z, %j, %lld, and other required constructs magically work (because you are no longer using the native printf, but the fixed mingw shim). Once you do that, you want to use __attribute__((__gnu_printf__)) instead of __attribute__((__printf__)) in order to teach gcc that yes, your use of %z is really going to work. For some more background reading: http://sourceforge.net/p/mingw-w64/wiki2/gnu%20printf/ https://lists.gnu.org/archive/html/bug-gnulib/2014-12/msg00029.html > --- > hw/ppc/spapr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 08401e0..9aaa800 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1438,7 +1438,7 @@ static void ppc_spapr_init(MachineState *machine) > } > if (spapr->rtas_size > RTAS_MAX_SIZE) { > hw_error("RTAS too big ! 0x%zx bytes (max is 0x%x)\n", > - spapr->rtas_size, RTAS_MAX_SIZE); > + (size_t)spapr->rtas_size, RTAS_MAX_SIZE); What's the actual compiler warning you got? This feels like it won't work if the real problem is the compiler telling you that %z is unknown; conversely, if it is a mismatch between 'size_t' vs. 'ssize_t', we probably ought to report it to the mingw folks to fix their environment to use the same underlying type for signed vs. unsigned sizes.
On 23 December 2014 at 22:50, Eric Blake <eblake@redhat.com> wrote: > What's the actual compiler warning you got? This feels like it won't > work if the real problem is the compiler telling you that %z is unknown; > conversely, if it is a mismatch between 'size_t' vs. 'ssize_t', we > probably ought to report it to the mingw folks to fix their environment > to use the same underlying type for signed vs. unsigned sizes. It complains: hw/ppc/spapr.c: In function ‘ppc_spapr_init’: hw/ppc/spapr.c:1441: warning: format ‘%zx’ expects type ‘size_t’, but argument 2 has type ‘ssize_t’ and unsurprisingly casting to size_t suppresses it. %zd gets me: hw/ppc/spapr.c:1441: warning: format ‘%zd’ expects type ‘signed size_t’, but argument 2 has type ‘ssize_t’ which is curious. (But we want the hex output anyway...) Grepping through the headers suggests we have typedef long _ssize_t; typedef _ssize_t ssize_t; I think 'size_t' ends up 'long unsigned int', though stddef.h is tricky to interpret because of all the macros. In any case, AIUI mingw isn't really maintained any more, and so the answer is either "do what is needed to shut up the compiler" or "declare mingw actually not supported and require mingw-w64"... -- PMM
Am 23.12.2014 um 23:47 schrieb Peter Maydell: > On 23 December 2014 at 22:36, Stefan Weil <sw@weilnetz.de> wrote: >> Am 23.12.2014 um 23:22 schrieb Peter Maydell: >>> --- a/hw/ppc/spapr.c >>> +++ b/hw/ppc/spapr.c >>> @@ -1438,7 +1438,7 @@ static void ppc_spapr_init(MachineState *machine) >>> } >>> if (spapr->rtas_size > RTAS_MAX_SIZE) { >>> hw_error("RTAS too big ! 0x%zx bytes (max is 0x%x)\n", >>> - spapr->rtas_size, RTAS_MAX_SIZE); >>> + (size_t)spapr->rtas_size, RTAS_MAX_SIZE); >>> exit(1); >>> } >>> g_free(filename); >> >> >> Which compiler did you use? I get no warning with Debian's >> x86_64-w64-mingw32-gcc 4.6.3 or >> native MinGW-w32 compilers. > > $ i586-mingw32msvc-gcc --version > i586-mingw32msvc-gcc (GCC) 4.2.1-sjlj (mingw32-2) > > Yes, this is ancient... it's from the Debian mingw32 package. > I just use this for compile testing, not for trying to run. > I should probably switch to the w64 compiler for build tests; > I forget now if there was a reason why I hadn't. > > I suspect, as I say, that this is just a generic old-gcc bug, > but it's the only one in the codebase, so it seems easiest > just to fix it. > > -- PMM "git grep" finds 6 "%zx", 66 "%zu" and 80 "%zd" in my QEMU source tree. Some of those are in debug traces, others are conditionally compiled depending on your configuration. Are you sure that none of those needs the same kind of modification, too? I don't thing fixing one of them for an ancient compiler is worth the trouble of explaining why there is a type cast. What about using hwaddr instead of ssize_t for rtas_size (and HWADDR_PRIx in the format string)? It looks like that would be more consistent with the rest of the code. See for example the arguments of function spapr_finalize_fdt. Stefan
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 08401e0..9aaa800 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -1438,7 +1438,7 @@ static void ppc_spapr_init(MachineState *machine) } if (spapr->rtas_size > RTAS_MAX_SIZE) { hw_error("RTAS too big ! 0x%zx bytes (max is 0x%x)\n", - spapr->rtas_size, RTAS_MAX_SIZE); + (size_t)spapr->rtas_size, RTAS_MAX_SIZE); exit(1); } g_free(filename);
The mingw32 compiler complains about trying to print variables of type ssize_t with the %z format string specifier. Since we're printing it as unsigned hex anyway, cast to size_t to silence the warning. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- I suspect that this is a compiler bug, but this is the only instance in the codebase so I'm prepared to work around it to get to a point where we can turn on warnings-as-errors for w32, because some of the w32-specific errors really are flagging up issues we need to fix. --- hw/ppc/spapr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)