Re: [PATCH v2 1/4] Add declare_object_symbol_alias for assembly codes (BZ #28128)

[Fangrui Song <maskray@google.com>]

On 2022-05-12, Adhemerval Zanella wrote:
>From: "H.J. Lu" <hjl.tools@gmail.com>
>
>There are 2 problems in:
>
> #define declare_symbol_alias(symbol, original, type, size) \
>  declare_symbol_alias_1 (symbol, original, type, size)
> #ifdef __ASSEMBLER__
> # define declare_symbol_alias_1(symbol, original, type, size) \
>   strong_alias (original, symbol); \
>   .type C_SYMBOL_NAME (symbol), %##type; \
>   .size C_SYMBOL_NAME (symbol), size
>
>1. .type and .size are substituted by arguments.
>2. %##type is expanded to "% type" due to the GCC bug:
>
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101613
>
>But assembler doesn't support "% type".
>
>Workaround BZ #28128 by
>
>1. Don't define declare_symbol_alias for assembly codes.
>2. Define declare_object_symbol_alias for assembly codes.

Interesting. clang -E can expand
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101613
correctly.

Reviewed-by: Fangrui Song <maskray@google.com>

>---
> include/libc-symbols.h | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
>diff --git a/include/libc-symbols.h b/include/libc-symbols.h
>index 662bd118b1..4bb3d8c7ba 100644
>--- a/include/libc-symbols.h
>+++ b/include/libc-symbols.h
>@@ -324,14 +324,16 @@ for linking")
>    This is only necessary when defining something in assembly, or playing
>    funny alias games where the size should be other than what the compiler
>    thinks it is.  */
>-#define declare_symbol_alias(symbol, original, type, size) \
>-  declare_symbol_alias_1 (symbol, original, type, size)
> #ifdef __ASSEMBLER__
>-# define declare_symbol_alias_1(symbol, original, type, size) \
>-   strong_alias (original, symbol); \
>-   .type C_SYMBOL_NAME (symbol), %##type; \
>-   .size C_SYMBOL_NAME (symbol), size
>+# define declare_object_symbol_alias(symbol, original, size) \
>+  declare_object_symbol_alias_1 (symbol, original, size)
>+# define declare_object_symbol_alias_1(symbol, original, s_size) \
>+   strong_alias (original, symbol) ASM_LINE_SEP \
>+   .type C_SYMBOL_NAME (symbol), %object ASM_LINE_SEP \
>+   .size C_SYMBOL_NAME (symbol), s_size ASM_LINE_SEP
> #else /* Not __ASSEMBLER__.  */
>+# define declare_symbol_alias(symbol, original, type, size) \
>+  declare_symbol_alias_1 (symbol, original, type, size)
> # define declare_symbol_alias_1(symbol, original, type, size) \
>    asm (".globl " __SYMBOL_PREFIX #symbol \
> 	"\n\t" declare_symbol_alias_1_alias (symbol, original) \
>-- 
>2.34.1
>