* [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
end of thread, other threads:[~2020-09-30 6:22 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 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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