diff options
| author | Eric Blake <eblake@redhat.com> | 2017-12-01 17:24:32 -0600 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-01-16 14:54:52 +0100 |
| commit | 2562755ee78983930d0662fa4d3bc5e2ac166350 (patch) | |
| tree | 0dd521d04be12d99cabc73ca928c862eabc0c348 /hw/char | |
| parent | 241187c11818e5223c4bdfac79f28fdf63731733 (diff) | |
maint: Fix macros with broken 'do/while(0); ' usage
The point of writing a macro embedded in a 'do { ... } while (0)'
loop (particularly if the macro has multiple statements or would
otherwise end with an 'if' statement) is so that the macro can be
used as a drop-in statement with the caller supplying the
trailing ';'. Although our coding style frowns on brace-less 'if':
if (cond)
statement;
else
something else;
that is the classic case where failure to use do/while(0) wrapping
would cause the 'else' to pair with any embedded 'if' in the macro
rather than the intended outer 'if'. But conversely, if the macro
includes an embedded ';', then the same brace-less coding style
would now have two statements, making the 'else' a syntax error
rather than pairing with the outer 'if'. Thus, even though our
coding style with required braces is not impacted, ending a macro
with ';' makes our code harder to port to projects that use
brace-less styles.
The change should have no semantic impact. I was not able to
fully compile-test all of the changes (as some of them are
examples of the ugly bit-rotting debug print statements that are
completely elided by default, and I didn't want to recompile
with the necessary -D witnesses - cleaning those up is left as a
bite-sized task for another day); I did, however, audit that for
all files touched, all callers of the changed macros DID supply
a trailing ';' at the callsite, and did not appear to be used
as part of a brace-less conditional.
Found mechanically via: $ git grep -B1 'while (0);' | grep -A1 \\\\
Signed-off-by: Eric Blake <eblake@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20171201232433.25193-7-eblake@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw/char')
| -rw-r--r-- | hw/char/cadence_uart.c | 2 | ||||
| -rw-r--r-- | hw/char/stm32f2xx_usart.c | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c index 6143494060..fbdbd463bb 100644 --- a/hw/char/cadence_uart.c +++ b/hw/char/cadence_uart.c @@ -33,7 +33,7 @@ #define DB_PRINT(...) do { \ fprintf(stderr, ": %s: ", __func__); \ fprintf(stderr, ## __VA_ARGS__); \ - } while (0); + } while (0) #else #define DB_PRINT(...) #endif diff --git a/hw/char/stm32f2xx_usart.c b/hw/char/stm32f2xx_usart.c index 268e435338..07b462d4b6 100644 --- a/hw/char/stm32f2xx_usart.c +++ b/hw/char/stm32f2xx_usart.c @@ -34,7 +34,7 @@ if (STM_USART_ERR_DEBUG >= lvl) { \ qemu_log("%s: " fmt, __func__, ## args); \ } \ -} while (0); +} while (0) #define DB_PRINT(fmt, args...) DB_PRINT_L(1, fmt, ## args) |