[FFmpeg-devel] [PATCH 2/2] x86inc: Clear __SECT__

Timothy Gu timothygu99 at gmail.com
Tue May 26 01:02:33 CEST 2015

This commit silences warning(s) like:

    libavcodec/x86/fft.asm:93: warning: section flags ignored on section

The cause of this warning is that because `struc` and `endstruc` attempts to
revert to the previous section state [1]. The section state is stored in the
macro __SECT__, defined by x86inc.asm to be `.note.GNU-stack ...`, through the
`SECTION` directive [2].  Thus, the `.note.GNU-stack` section is defined twice
(once in x86inc.asm, once during `endstruc`), causing the warning.

That is the first part of the commit: using the primitive `[section]` format
for .note.GNU-stack etc., which does not update `__SECT__` [2].

That fixes only half of the problem. Even without any `SECTION` directives,
`__SECT__` is predefined as `.text`, which conflicting with the later
`SECTION_TEXT` (which expands to `.text align=16`).

[1]: http://www.nasm.us/doc/nasmdoc6.html#section-6.4
[2]: http://www.nasm.us/doc/nasmdoc6.html#section-6.3

Better patch as suggested by Ronald.

 libavutil/x86/x86inc.asm | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavutil/x86/x86inc.asm b/libavutil/x86/x86inc.asm
index f1b4b85..12779f5 100644
--- a/libavutil/x86/x86inc.asm
+++ b/libavutil/x86/x86inc.asm
@@ -722,9 +722,13 @@ BRANCH_INSTR jz, je, jnz, jne, jl, jle, jnl, jnle, jg, jge, jng, jnge, ja, jae,
 ; This is needed for ELF, otherwise the GNU linker assumes the stack is
 ; executable by default.
 %ifidn __OUTPUT_FORMAT__,elf
-SECTION .note.GNU-stack noalloc noexec nowrite progbits
+[section .note.GNU-stack noalloc noexec nowrite progbits]
+; Overrides the default .text section.
+; Silences warnings when defining structures.
+%define __SECT__
 ; cpuflags
 %assign cpuflags_mmx      (1<<0)

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