On 4/2/25 19:24, Roman Bogorodskiy wrote: > The 'plain' optimization type also triggers the clang stack frame size > issues, so increase limit for it as well. > > Signed-off-by: Roman Bogorodskiy <bogorodskiy(a)gmail.com&gt; > --- > meson.build | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/meson.build b/meson.build > index 56823ca25b..0a402a19a2 100644 > --- a/meson.build > +++ b/meson.build > @@ -259,7 +259,7 @@ alloc_max = run_command( > stack_frame_size = 2048 > > # clang without optimization enlarges stack frames in certain corner cases > -if cc.get_id() == 'clang' and get_option('optimization') == '0' > +if cc.get_id() == 'clang' and get_option('optimization') in ['plain', '0'] > stack_frame_size = 4096 > endif > Funny, with clang I hit this issue for all possible values of --optimization {plain,0,g,1,2,3,s}. I worry this is clang version dependent. Should we just drop check for 'optimization' argument altogether?

Michal Prívozník wrote: > On 4/2/25 19:24, Roman Bogorodskiy wrote: >> The 'plain' optimization type also triggers the clang stack frame size >> issues, so increase limit for it as well. >> >> Signed-off-by: Roman Bogorodskiy <bogorodskiy(a)gmail.com&gt; >> --- >> meson.build | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/meson.build b/meson.build >> index 56823ca25b..0a402a19a2 100644 >> --- a/meson.build >> +++ b/meson.build >> @@ -259,7 +259,7 @@ alloc_max = run_command( >> stack_frame_size = 2048 >> >> # clang without optimization enlarges stack frames in certain corner cases >> -if cc.get_id() == 'clang' and get_option('optimization') == '0' >> +if cc.get_id() == 'clang' and get_option('optimization') in ['plain', '0'] >> stack_frame_size = 4096 >> endif >> > > Funny, with clang I hit this issue for all possible values of > --optimization {plain,0,g,1,2,3,s}. That's interesting indeed. Currently, "plain" is the only value that triggers the issue for me: Problematic file is the following: ../src/remote/remote_driver.c:790:1: error: stack frame size (2344) exceeds limit (2048) in 'doRemoteOpen' [-Werror,-Wframe-larger-than] 790 | doRemoteOpen(virConnectPtr conn, | ^ 1 error generated. Clang version is 19.1.7.

On 4/4/25 08:46, Michal Prívozník wrote: > On 4/3/25 18:28, Roman Bogorodskiy wrote: >> Michal Prívozník wrote: >> >>> On 4/2/25 19:24, Roman Bogorodskiy wrote: >>>> The 'plain' optimization type also triggers the clang stack frame size >>>> issues, so increase limit for it as well. >>>> >>>> Signed-off-by: Roman Bogorodskiy <bogorodskiy(a)gmail.com&gt; >>>> --- >>>> meson.build | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/meson.build b/meson.build >>>> index 56823ca25b..0a402a19a2 100644 >>>> --- a/meson.build >>>> +++ b/meson.build >>>> @@ -259,7 +259,7 @@ alloc_max = run_command( >>>> stack_frame_size = 2048 >>>> >>>> # clang without optimization enlarges stack frames in certain corner cases >>>> -if cc.get_id() == 'clang' and get_option('optimization') == '0' >>>> +if cc.get_id() == 'clang' and get_option('optimization') in ['plain', '0'] >>>> stack_frame_size = 4096 >>>> endif >>>> >>> >>> Funny, with clang I hit this issue for all possible values of >>> --optimization {plain,0,g,1,2,3,s}. >> >> That's interesting indeed. >> >> Currently, "plain" is the only value that triggers the issue for me: >> >> Problematic file is the following: >> >> ../src/remote/remote_driver.c:790:1: error: stack frame size (2344) exceeds limit (2048) in 'doRemoteOpen' [-Werror,-Wframe-larger-than] >> 790 | doRemoteOpen(virConnectPtr conn, >> | ^ >> 1 error generated. >> >> Clang version is 19.1.7. > > Same here: > > clang version 19.1.7 > Target: x86_64-pc-linux-gnu > > except I'm running Linux and I assume you're running *BSD. Given what > also Dan said, are you willing to post a v2 where the condition is > simplified to just 'clang' and no get_option('optimization')? > > Actually, give me a minute or to - maybe there's something I can do > about doRemoteOpen() so that its stack isn't that huge. Alight, I think I know what's going on and why we're getting 2300+ bytes long stack even with just a few variables declared. Shortly: it's because of glib. Longer version: glib declares plenty of helper variables (mostly for type checking). For instance: g_clear_pointer() is declared as: #define g_clear_pointer(pp, destroy) \ G_STMT_START \ { \ G_STATIC_ASSERT (sizeof *(pp) == sizeof (gpointer)); \ glib_typeof ((pp)) _pp = (pp); \ glib_typeof (*(pp)) _ptr = *_pp; \ *_pp = NULL; \ if (_ptr) \ (destroy) (_ptr); \ } \ G_STMT_END \ And our VIR_FREE() is defined to be g_clear_pointer(). Then, g_strdup() is defined to be g_strdup_inline(), which: a) is declared as always inline, and b) declares two additional variables: G_ALWAYS_INLINE static inline char * g_strdup_inline (const char *str) { if (__builtin_constant_p (!str) && !str) return NULL; if (__builtin_constant_p (!!str) && !!str && __builtin_constant_p (strlen (str))) { const size_t len = strlen (str) + 1; char *dup_str = (char *) g_malloc (len); return (char *) memcpy (dup_str, str, len); } return g_strdup (str); } And finally, for some reason, attribute cleanup also increases stack size (observed by playing with godbolt.org) - but this is for both gcc and clang and isn't glib related. Honestly, I do not understand why attribute cleanup would need to increase stack size, but whatever. I think now I have all the ingredients needed to break the function down into smaller pieces. So hopefully, in the end, this whole workaround might be dropped. NB: there's still vboxSnapshotRedefine() which has even bigger stack: ../src/vbox/vbox_common.c:4557:1: error: stack frame size (2824) exceeds limit (2048) in 'vboxSnapshotRedefine' [-Werror,-Wframe-larger-than] but I think (wishfully) the same strategy can be applied there.