| Message ID | 20221102202258.456359-1-sw@weilnetz.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [for,7.2] Fix broken configure with -Wunused-parameter | expand |
On Wed, Nov 02, 2022 at 09:22:58PM +0100, Stefan Weil via wrote: > The configure script fails because it tries to compile small C programs > with a main function which is declared with arguments argc and argv > although those arguments are unused. > > Running `configure -extra-cflags=-Wunused-parameter` triggers the problem. > configure for a native build does abort but shows the error in config.log. > A cross build configure for Windows with Debian stable aborts with an > error. > > Avoiding unused arguments fixes this. I'm not convinced that we should allow -extra-cflags to influence the configure compile checks at all, as there are likely more cases where arbitrary -W$warn flag will impact the checks, potentially causing configure to silently take the wrong action. > > Signed-off-by: Stefan Weil <sw@weilnetz.de> > --- > > See https://gitlab.com/qemu-project/qemu/-/issues/1295. > > I noticed the problem because I often compile with -Wextra. > > Stefan > > configure | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/configure b/configure > index 4275f5419f..1106c04fea 100755 > --- a/configure > +++ b/configure > @@ -1258,6 +1258,7 @@ if test "$stack_protector" != "no"; then > cat > $TMPC << EOF > int main(int argc, char *argv[]) > { > + (void)argc; > char arr[64], *p = arr, *c = argv[0]; > while (*c) { > *p++ = *c++; > @@ -1607,7 +1608,7 @@ fi > > if test "$safe_stack" = "yes"; then > cat > $TMPC << EOF > -int main(int argc, char *argv[]) > +int main(void) > { > #if ! __has_feature(safe_stack) > #error SafeStack Disabled > @@ -1629,7 +1630,7 @@ EOF > fi > else > cat > $TMPC << EOF > -int main(int argc, char *argv[]) > +int main(void) > { > #if defined(__has_feature) > #if __has_feature(safe_stack) > @@ -1675,7 +1676,7 @@ static const int Z = 1; > #define TAUT(X) ((X) == Z) > #define PAREN(X, Y) (X == Y) > #define ID(X) (X) > -int main(int argc, char *argv[]) > +int main(void) > { > int x = 0, y = 0; > x = ID(x); > -- > 2.30.2 > > With regards, Daniel
Am 03.11.22 um 09:58 schrieb Daniel P. Berrangé: > On Wed, Nov 02, 2022 at 09:22:58PM +0100, Stefan Weil via wrote: >> The configure script fails because it tries to compile small C programs >> with a main function which is declared with arguments argc and argv >> although those arguments are unused. >> >> Running `configure -extra-cflags=-Wunused-parameter` triggers the problem. >> configure for a native build does abort but shows the error in config.log. >> A cross build configure for Windows with Debian stable aborts with an >> error. >> >> Avoiding unused arguments fixes this. > I'm not convinced that we should allow -extra-cflags to influence > the configure compile checks at all, as there are likely more cases > where arbitrary -W$warn flag will impact the checks, potentially > causing configure to silently take the wrong action. I partially agree, but configure should fail if invalid -extra-cflags are specified, and the checks must also respect additional include paths given by -extra-cflags of course. And I think that the changes in my patch are an improvement in any case. Stefan
On Wed, 2 Nov 2022 at 20:24, Stefan Weil via <qemu-devel@nongnu.org> wrote: > > The configure script fails because it tries to compile small C programs > with a main function which is declared with arguments argc and argv > although those arguments are unused. > > Running `configure -extra-cflags=-Wunused-parameter` triggers the problem. > configure for a native build does abort but shows the error in config.log. > A cross build configure for Windows with Debian stable aborts with an > error. > > Avoiding unused arguments fixes this. > > Signed-off-by: Stefan Weil <sw@weilnetz.de> > --- > > See https://gitlab.com/qemu-project/qemu/-/issues/1295. > > I noticed the problem because I often compile with -Wextra. > > Stefan > > configure | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/configure b/configure > index 4275f5419f..1106c04fea 100755 > --- a/configure > +++ b/configure > @@ -1258,6 +1258,7 @@ if test "$stack_protector" != "no"; then > cat > $TMPC << EOF > int main(int argc, char *argv[]) > { > + (void)argc; I'm not a huge fan of this syntax, and it doesn't match the way we deal with "argument is unused" elsewhere in the codebase (where we either don't care about it or else use the GCC 'unused' attribute hidden behind the glib G_GNUC_UNUSED macro). I am surprised that this didn't get caught by the check in do_compiler_werror(), which is supposed to report "this configure test passed without -Werror but failed with -Werror, so configure is probably buggy.". That's what's supposed to catch "your compiler warns on stuff our doesn't in the test case programs". If you're building with --disable-werror then configure should be OK anyway. This is probably a good idea if you want to build with extra warning arguments in --extra-cflags. If it doesn't work right even with --disable-werror that's also something we should investigate. > char arr[64], *p = arr, *c = argv[0]; > while (*c) { > *p++ = *c++; > @@ -1607,7 +1608,7 @@ fi > > if test "$safe_stack" = "yes"; then > cat > $TMPC << EOF > -int main(int argc, char *argv[]) > +int main(void) > { > #if ! __has_feature(safe_stack) > #error SafeStack Disabled > @@ -1629,7 +1630,7 @@ EOF > fi > else > cat > $TMPC << EOF > -int main(int argc, char *argv[]) > +int main(void) > { > #if defined(__has_feature) > #if __has_feature(safe_stack) > @@ -1675,7 +1676,7 @@ static const int Z = 1; > #define TAUT(X) ((X) == Z) > #define PAREN(X, Y) (X == Y) > #define ID(X) (X) > -int main(int argc, char *argv[]) > +int main(void) > { > int x = 0, y = 0; > x = ID(x); No objection to the cases where we can pass "void", that's a neater way to write the test anyway. thanks -- PMM
Am 03.11.22 um 12:48 schrieb Peter Maydell: > On Wed, 2 Nov 2022 at 20:24, Stefan Weil via <qemu-devel@nongnu.org> wrote: >> The configure script fails because it tries to compile small C programs >> with a main function which is declared with arguments argc and argv >> although those arguments are unused. >> >> Running `configure -extra-cflags=-Wunused-parameter` triggers the problem. >> configure for a native build does abort but shows the error in config.log. >> A cross build configure for Windows with Debian stable aborts with an >> error. >> >> Avoiding unused arguments fixes this. >> >> Signed-off-by: Stefan Weil <sw@weilnetz.de> >> --- >> >> See https://gitlab.com/qemu-project/qemu/-/issues/1295. >> >> I noticed the problem because I often compile with -Wextra. >> >> Stefan >> >> configure | 7 ++++--- >> 1 file changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/configure b/configure >> index 4275f5419f..1106c04fea 100755 >> --- a/configure >> +++ b/configure >> @@ -1258,6 +1258,7 @@ if test "$stack_protector" != "no"; then >> cat > $TMPC << EOF >> int main(int argc, char *argv[]) >> { >> + (void)argc; > I'm not a huge fan of this syntax, and it doesn't match the way > we deal with "argument is unused" elsewhere in the codebase > (where we either don't care about it or else use the GCC 'unused' > attribute hidden behind the glib G_GNUC_UNUSED macro). Any other variant is also fine for me, for example "using" argc by a "return argc == 0;" instead of "return 0;". Would that be better? If there is an accepted variant, I can either send a v2 patch, or maybe such a trivial change can be applied when merging. > I am surprised that this didn't get caught by the check in > do_compiler_werror(), which is supposed to report "this > configure test passed without -Werror but failed with > -Werror, so configure is probably buggy.". That's what's > supposed to catch "your compiler warns on stuff our doesn't > in the test case programs". > > If you're building with --disable-werror then configure > should be OK anyway. This is probably a good idea if you want > to build with extra warning arguments in --extra-cflags. > If it doesn't work right even with --disable-werror that's > also something we should investigate. Cross builds for Windows fail with and without --disable-werror. See also my bug report https://gitlab.com/qemu-project/qemu/-/issues/1295. You are right that this is strange and should be investigated, especially because native builds don't fail like that. >> char arr[64], *p = arr, *c = argv[0]; >> while (*c) { >> *p++ = *c++; >> @@ -1607,7 +1608,7 @@ fi >> >> if test "$safe_stack" = "yes"; then >> cat > $TMPC << EOF >> -int main(int argc, char *argv[]) >> +int main(void) >> { >> #if ! __has_feature(safe_stack) >> #error SafeStack Disabled >> @@ -1629,7 +1630,7 @@ EOF >> fi >> else >> cat > $TMPC << EOF >> -int main(int argc, char *argv[]) >> +int main(void) >> { >> #if defined(__has_feature) >> #if __has_feature(safe_stack) >> @@ -1675,7 +1676,7 @@ static const int Z = 1; >> #define TAUT(X) ((X) == Z) >> #define PAREN(X, Y) (X == Y) >> #define ID(X) (X) >> -int main(int argc, char *argv[]) >> +int main(void) >> { >> int x = 0, y = 0; >> x = ID(x); > No objection to the cases where we can pass "void", that's > a neater way to write the test anyway. > > thanks > -- PMM >
On 11/3/22 09:58, Daniel P. Berrangé wrote: > On Wed, Nov 02, 2022 at 09:22:58PM +0100, Stefan Weil via wrote: >> The configure script fails because it tries to compile small C programs >> with a main function which is declared with arguments argc and argv >> although those arguments are unused. >> >> Running `configure -extra-cflags=-Wunused-parameter` triggers the problem. >> configure for a native build does abort but shows the error in config.log. >> A cross build configure for Windows with Debian stable aborts with an >> error. >> >> Avoiding unused arguments fixes this. > I'm not convinced that we should allow -extra-cflags to influence > the configure compile checks at all, as there are likely more cases > where arbitrary -W$warn flag will impact the checks, potentially > causing configure to silently take the wrong action. Meson cc.compiles/cc.links tests never use -Werror to avoid this (which has a different set of issues, but if you want you can add the argument manually and 0.64 will also add a "werror: true|false" argument). Since the last configure tests will go away in 8.0, I'm fine with just applying this patch in the meanwhile. Paolo
On 11/2/22 21:22, Stefan Weil via wrote: > != "no"; then > cat > $TMPC << EOF > int main(int argc, char *argv[]) > { > + (void)argc; > char arr[64], *p = arr, *c = argv[0]; You could use argv[argc - 1] instead. Paolo > while (*c) { > *p++ = *c++;
diff --git a/configure b/configure index 4275f5419f..1106c04fea 100755 --- a/configure +++ b/configure @@ -1258,6 +1258,7 @@ if test "$stack_protector" != "no"; then cat > $TMPC << EOF int main(int argc, char *argv[]) { + (void)argc; char arr[64], *p = arr, *c = argv[0]; while (*c) { *p++ = *c++; @@ -1607,7 +1608,7 @@ fi if test "$safe_stack" = "yes"; then cat > $TMPC << EOF -int main(int argc, char *argv[]) +int main(void) { #if ! __has_feature(safe_stack) #error SafeStack Disabled @@ -1629,7 +1630,7 @@ EOF fi else cat > $TMPC << EOF -int main(int argc, char *argv[]) +int main(void) { #if defined(__has_feature) #if __has_feature(safe_stack) @@ -1675,7 +1676,7 @@ static const int Z = 1; #define TAUT(X) ((X) == Z) #define PAREN(X, Y) (X == Y) #define ID(X) (X) -int main(int argc, char *argv[]) +int main(void) { int x = 0, y = 0; x = ID(x);
The configure script fails because it tries to compile small C programs with a main function which is declared with arguments argc and argv although those arguments are unused. Running `configure -extra-cflags=-Wunused-parameter` triggers the problem. configure for a native build does abort but shows the error in config.log. A cross build configure for Windows with Debian stable aborts with an error. Avoiding unused arguments fixes this. Signed-off-by: Stefan Weil <sw@weilnetz.de> --- See https://gitlab.com/qemu-project/qemu/-/issues/1295. I noticed the problem because I often compile with -Wextra. Stefan configure | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)