| Message ID | 20240817134325.AA09E33E87@hamza.pair.com |
|---|---|
| State | New |
| Headers | show |
| Series | [pushed] wwwdocs: gcc-15: Mark an AVR instruction up as <code> | expand |
Am 17.08.24 um 15:43 schrieb Gerald Pfeifer: > All this patch does (modulo reformatting) is put SEI in a <code> > environment. > > However, looking at this I've got a question: How about "imposing a > function name" which is listed as a difference of <code>noblock</code> > versus others? This (the specific name) is not actually documented > anywhere? Is that an omission, or am I missing something? > > Gerald Hmmm, as far as I know, there is no documentation. The GCC docs just propose to use the ISR resp. ISR_N macro from AVR-LibC, and AVR-LibC doesn't document the gory details, either: https://avrdudes.github.io/avr-libc/avr-libc-user-manual-2.2.0/group__avr__interrupts.html#gad28590624d422cdf30d626e0a506255f Background is this: The old signal and interrupt attributes allow to define an ISR as 1) [[signal]] void __vector_1 (void) { ... } 2) [[interrupt]] void __vector_2 (void) { ... } where the 2nd form adds a SEI before the prologue. Using AVR-LibC, the idioms for 1) and 2) are: 3) ISR(1) { ... } 4) ISR(2, ISR_NOBLOCK) { ... } where 4) basically resolves to [[signal,interrupt]] void __vector_2 ... This is supported by GCC: With [[interrupt]], the [[signal]] part is basically ignored. This won't work with the new signal(n) attribute: 5) ISR_N(1) static void my_isr1 (void) { ... } // Ok 6) ISR_N(2, ISR_NOBLOCK) static void my_isr2 (void) { ... } // Won't work as expected when we expand "ISR_NOBLOCK" as [[interrupt]] because the latter requires a function name of the __vector_N form like in 2). Hence a new attribute "noblock" without that requirement. HTH Johann p.s.: ISR_N is added in AVR-LibC v2.3, so you won't find the doc behind the link above. > --- > htdocs/gcc-15/changes.html | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/htdocs/gcc-15/changes.html b/htdocs/gcc-15/changes.html > index bfd98496..fe7cf3c1 100644 > --- a/htdocs/gcc-15/changes.html > +++ b/htdocs/gcc-15/changes.html > @@ -122,11 +122,11 @@ a work-in-progress.</p> > functions defined in a C++ namespace.</li> > <li>Support has been added for the <code>noblock</code> function attribute. > It can be specified together with the <code>signal</code> attribute to > - indicate that the interrupt service routine should start with a SEI > - instruction to globally re-enable interrupts. The difference to the > - <code>interrupt</code> attribute is that the <code>noblock</code> > - attribute just acts like a flag and does not impose a specific function > - name.</li> > + indicate that the interrupt service routine should start with a > + <code>SEI</code> instruction to globally re-enable interrupts. > + The difference to the <code>interrupt</code> attribute is that the > + <code>noblock</code> attribute just acts like a flag and does not > + impose a specific function name.</li> > <li>Support has been added for the <code>__builtin_avr_mask1</code> > <a href="https://gcc.gnu.org/onlinedocs/gcc/AVR-Built-in-Functions.html#index-_005f_005fbuiltin_005favr_005fmask1" > >built-in function</a>. It can be used to compute some bit masks when
diff --git a/htdocs/gcc-15/changes.html b/htdocs/gcc-15/changes.html index bfd98496..fe7cf3c1 100644 --- a/htdocs/gcc-15/changes.html +++ b/htdocs/gcc-15/changes.html @@ -122,11 +122,11 @@ a work-in-progress.</p> functions defined in a C++ namespace.</li> <li>Support has been added for the <code>noblock</code> function attribute. It can be specified together with the <code>signal</code> attribute to - indicate that the interrupt service routine should start with a SEI - instruction to globally re-enable interrupts. The difference to the - <code>interrupt</code> attribute is that the <code>noblock</code> - attribute just acts like a flag and does not impose a specific function - name.</li> + indicate that the interrupt service routine should start with a + <code>SEI</code> instruction to globally re-enable interrupts. + The difference to the <code>interrupt</code> attribute is that the + <code>noblock</code> attribute just acts like a flag and does not + impose a specific function name.</li> <li>Support has been added for the <code>__builtin_avr_mask1</code> <a href="https://gcc.gnu.org/onlinedocs/gcc/AVR-Built-in-Functions.html#index-_005f_005fbuiltin_005favr_005fmask1" >built-in function</a>. It can be used to compute some bit masks when