* [PATCH] Fix a warning when initializing symbol_flags
@ 2020-09-26 0:42 Saagar Jha
2020-09-26 13:06 ` Alan Modra
0 siblings, 1 reply; 6+ messages in thread
From: Saagar Jha @ 2020-09-26 0:42 UTC (permalink / raw)
To: binutils; +Cc: Saagar Jha
Clang on certain platforms (such as arm64) will warn if a struct is
partially initialized:
symbols.c:199:35: error: missing field 'written' initializer [-Werror,-Wmissing-field-initializers]
2895 symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
If we use empty braces we have the same effect but avoid the warning.
gas/ChangeLog:
* symbols.c: Shorten an initializer for symbol_flags to be empty.
---
gas/ChangeLog | 4 ++++
gas/symbols.c | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/gas/ChangeLog b/gas/ChangeLog
index 1c692dd931..6f9e842330 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,7 @@
+2020-09-25 Saagar Jha <saagar@saagarjha.com>
+
+ * symbols.c: Shorten an initializer for symbol_flags to be empty.
+
2020-09-24 Jim Wilson <jimw@sifive.com>
PR 26400
diff --git a/gas/symbols.c b/gas/symbols.c
index d6080886be..40d7ebc586 100644
--- a/gas/symbols.c
+++ b/gas/symbols.c
@@ -196,7 +196,7 @@ static void *
symbol_entry_find (htab_t table, const char *name)
{
hashval_t hash = htab_hash_string (name);
- symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
+ symbol_entry_t needle = { { { }, hash, name, 0, 0, 0 } };
return htab_find_with_hash (table, &needle, hash);
}
--
2.28.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix a warning when initializing symbol_flags
2020-09-26 0:42 [PATCH] Fix a warning when initializing symbol_flags Saagar Jha
@ 2020-09-26 13:06 ` Alan Modra
2020-09-26 19:21 ` Hans-Peter Nilsson
0 siblings, 1 reply; 6+ messages in thread
From: Alan Modra @ 2020-09-26 13:06 UTC (permalink / raw)
To: Saagar Jha; +Cc: binutils
On Fri, Sep 25, 2020 at 05:42:24PM -0700, Saagar Jha wrote:
> Clang on certain platforms (such as arm64) will warn if a struct is
> partially initialized:
>
> symbols.c:199:35: error: missing field 'written' initializer [-Werror,-Wmissing-field-initializers]
> 2895 symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
>
> If we use empty braces we have the same effect but avoid the warning.
But on gcc-4.9 this results in:
symbols.c: In function ‘symbol_entry_find’:
symbols.c:199:3: error: missing initializer for field ‘local_symbol’ of ‘struct symbol_flags’ [-Werror=missing-field-initializers]
symbol_entry_t needle = { { { }, hash, name, 0, 0, 0 } };
^
symbols.c:39:16: note: ‘local_symbol’ declared here
unsigned int local_symbol : 1;
^
So I don't think we should apply your patch.
--
Alan Modra
Australia Development Lab, IBM
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix a warning when initializing symbol_flags
2020-09-26 13:06 ` Alan Modra
@ 2020-09-26 19:21 ` Hans-Peter Nilsson
2020-09-26 22:30 ` Saagar Jha
0 siblings, 1 reply; 6+ messages in thread
From: Hans-Peter Nilsson @ 2020-09-26 19:21 UTC (permalink / raw)
To: Alan Modra; +Cc: Saagar Jha, binutils
On Sat, 26 Sep 2020, Alan Modra via Binutils wrote:
> On Fri, Sep 25, 2020 at 05:42:24PM -0700, Saagar Jha wrote:
> > Clang on certain platforms (such as arm64) will warn if a struct is
> > partially initialized:
> >
> > symbols.c:199:35: error: missing field 'written' initializer [-Werror,-Wmissing-field-initializers]
> > 2895 symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
> >
> > If we use empty braces we have the same effect but avoid the warning.
>
> But on gcc-4.9 this results in:
>
> symbols.c: In function ?symbol_entry_find?:
> symbols.c:199:3: error: missing initializer for field ?local_symbol? of ?struct symbol_flags? [-Werror=missing-field-initializers]
> symbol_entry_t needle = { { { }, hash, name, 0, 0, 0 } };
> ^
> symbols.c:39:16: note: ?local_symbol? declared here
> unsigned int local_symbol : 1;
> ^
>
> So I don't think we should apply your patch.
How about a memset 0 and setting .hash and .name?
I had to do that locally for an older gcc, that had a similar
warning. I prefered that over 11 (IIRC) "0," and having to
keep them straight. :)
brgds, H-P
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix a warning when initializing symbol_flags
2020-09-26 19:21 ` Hans-Peter Nilsson
@ 2020-09-26 22:30 ` Saagar Jha
2020-09-30 6:12 ` Alan Modra
0 siblings, 1 reply; 6+ messages in thread
From: Saagar Jha @ 2020-09-26 22:30 UTC (permalink / raw)
To: Hans-Peter Nilsson; +Cc: Alan Modra, binutils
Ah, so I just realized that this file is actually compiled as C and not a C++ file in .c clothing, so even if this didn’t warn in Clang the patch was still incorrect as {} is an invalid initializer in C and GCC is correct in flagging it (though perhaps not for the right reasons). Newer versions of Clang do correctly identify { 0 } as the correct zero initialization idiom: https://github.com/llvm/llvm-project/commit/817a3bfcdd0bbac8d74fdfdb83a08484d8f63a30, although most distributions seem to carry a version older than this.
Eleven zeroes is, as far as I can tell, the only widely-compatible, guaranteed-to-work way to initialize this without warnings. memset would generally “work” but if we’re being pedantic I believe this has only been guaranteed as of a recent C standard (C11?) So I guess I’ll have to defer to whatever the decision is here on portability versus readability. (Third option: disable the warning around this code, perhaps after checking theg version.)
> On Sep 26, 2020, at 12:21, Hans-Peter Nilsson <hp@bitrange.com> wrote:
>
> On Sat, 26 Sep 2020, Alan Modra via Binutils wrote:
>
>> On Fri, Sep 25, 2020 at 05:42:24PM -0700, Saagar Jha wrote:
>>> Clang on certain platforms (such as arm64) will warn if a struct is
>>> partially initialized:
>>>
>>> symbols.c:199:35: error: missing field 'written' initializer [-Werror,-Wmissing-field-initializers]
>>> 2895 symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
>>>
>>> If we use empty braces we have the same effect but avoid the warning.
>>
>> But on gcc-4.9 this results in:
>>
>> symbols.c: In function ?symbol_entry_find?:
>> symbols.c:199:3: error: missing initializer for field ?local_symbol? of ?struct symbol_flags? [-Werror=missing-field-initializers]
>> symbol_entry_t needle = { { { }, hash, name, 0, 0, 0 } };
>> ^
>> symbols.c:39:16: note: ?local_symbol? declared here
>> unsigned int local_symbol : 1;
>> ^
>>
>> So I don't think we should apply your patch.
>
> How about a memset 0 and setting .hash and .name?
>
> I had to do that locally for an older gcc, that had a similar
> warning. I prefered that over 11 (IIRC) "0," and having to
> keep them straight. :)
>
> brgds, H-P
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix a warning when initializing symbol_flags
2020-09-26 22:30 ` Saagar Jha
@ 2020-09-30 6:12 ` Alan Modra
2020-09-30 6:22 ` Saagar Jha
0 siblings, 1 reply; 6+ messages in thread
From: Alan Modra @ 2020-09-30 6:12 UTC (permalink / raw)
To: Saagar Jha; +Cc: Hans-Peter Nilsson, binutils
On Sat, Sep 26, 2020 at 03:30:53PM -0700, Saagar Jha wrote:
> Eleven zeroes is, as far as I can tell, the only widely-compatible,
> guaranteed-to-work way to initialize this without warnings.
Let's do that. I had reason today to compile binutils on an older
system with gcc-4.4.7 installed, and that warned on the current
source.
* config/obj-elf.c (obj_elf_change_section): Rename variable to
avoid shadowing warning.
* symbols.c (symbol_entry_find): Init all symbol_flags fields.
diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c
index b1c99020a3..cd457abe5e 100644
--- a/gas/config/obj-elf.c
+++ b/gas/config/obj-elf.c
@@ -762,8 +762,8 @@ obj_elf_change_section (const char *name,
/* We could be repurposing an undefined symbol here: make sure we
reset sy_value to look like other section symbols in order to avoid
trying to incorrectly resolve this section symbol later on. */
- static const expressionS expr = { .X_op = O_constant };
- symbol_set_value_expression (secsym, &expr);
+ static const expressionS exp = { .X_op = O_constant };
+ symbol_set_value_expression (secsym, &exp);
symbol_set_bfdsym (secsym, sec->symbol);
}
else
diff --git a/gas/symbols.c b/gas/symbols.c
index d6080886be..26dd84b126 100644
--- a/gas/symbols.c
+++ b/gas/symbols.c
@@ -196,7 +196,8 @@ static void *
symbol_entry_find (htab_t table, const char *name)
{
hashval_t hash = htab_hash_string (name);
- symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
+ symbol_entry_t needle = { { { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
+ hash, name, 0, 0, 0 } };
return htab_find_with_hash (table, &needle, hash);
}
--
Alan Modra
Australia Development Lab, IBM
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Fix a warning when initializing symbol_flags
2020-09-30 6:12 ` Alan Modra
@ 2020-09-30 6:22 ` Saagar Jha
0 siblings, 0 replies; 6+ messages in thread
From: Saagar Jha @ 2020-09-30 6:22 UTC (permalink / raw)
To: Alan Modra; +Cc: binutils
Actually, you just reminded me of one more way to do this, although it’s a bit cryptic:
static struct symbol_flags zero_flags;
symbol_entry_t needle = { { zero_flags, hash, name, 0, 0, 0 } };
I had made a patch for this over the weekend but alas I forgot to send it to the list. But if you’re fine with the zeroes, that’s OK too.
Saagar Jha
> On Sep 29, 2020, at 23:12, Alan Modra <amodra@gmail.com> wrote:
>
> On Sat, Sep 26, 2020 at 03:30:53PM -0700, Saagar Jha wrote:
>> Eleven zeroes is, as far as I can tell, the only widely-compatible,
>> guaranteed-to-work way to initialize this without warnings.
>
> Let's do that. I had reason today to compile binutils on an older
> system with gcc-4.4.7 installed, and that warned on the current
> source.
>
> * config/obj-elf.c (obj_elf_change_section): Rename variable to
> avoid shadowing warning.
> * symbols.c (symbol_entry_find): Init all symbol_flags fields.
>
> diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c
> index b1c99020a3..cd457abe5e 100644
> --- a/gas/config/obj-elf.c
> +++ b/gas/config/obj-elf.c
> @@ -762,8 +762,8 @@ obj_elf_change_section (const char *name,
> /* We could be repurposing an undefined symbol here: make sure we
> reset sy_value to look like other section symbols in order to avoid
> trying to incorrectly resolve this section symbol later on. */
> - static const expressionS expr = { .X_op = O_constant };
> - symbol_set_value_expression (secsym, &expr);
> + static const expressionS exp = { .X_op = O_constant };
> + symbol_set_value_expression (secsym, &exp);
> symbol_set_bfdsym (secsym, sec->symbol);
> }
> else
> diff --git a/gas/symbols.c b/gas/symbols.c
> index d6080886be..26dd84b126 100644
> --- a/gas/symbols.c
> +++ b/gas/symbols.c
> @@ -196,7 +196,8 @@ static void *
> symbol_entry_find (htab_t table, const char *name)
> {
> hashval_t hash = htab_hash_string (name);
> - symbol_entry_t needle = { { { 0 }, hash, name, 0, 0, 0 } };
> + symbol_entry_t needle = { { { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
> + hash, name, 0, 0, 0 } };
> return htab_find_with_hash (table, &needle, hash);
> }
>
>
>
> --
> Alan Modra
> Australia Development Lab, IBM
^ permalink raw reply [flat|nested] 6+ messages in thread
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2020-09-26 0:42 [PATCH] Fix a warning when initializing symbol_flags Saagar Jha
2020-09-26 13:06 ` Alan Modra
2020-09-26 19:21 ` Hans-Peter Nilsson
2020-09-26 22:30 ` Saagar Jha
2020-09-30 6:12 ` Alan Modra
2020-09-30 6:22 ` Saagar Jha
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