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Diffstat (limited to 'gas/doc/as.texinfo')
| -rw-r--r-- | gas/doc/as.texinfo | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo index 9871fe2..e4f7984 100644 --- a/gas/doc/as.texinfo +++ b/gas/doc/as.texinfo @@ -4308,16 +4308,23 @@ absolute expression. If @code{@value{LD}} sees multiple common symbols with the same name, and they do not all have the same size, it will allocate space using the largest size. -@ifset ELF -When using ELF, the @code{.comm} directive takes an optional third argument. -This is the desired alignment of the symbol, specified as a byte boundary (for -example, an alignment of 16 means that the least significant 4 bits of the -address should be zero). The alignment must be an absolute expression, and it -must be a power of two. If @code{@value{LD}} allocates uninitialized memory -for the common symbol, it will use the alignment when placing the symbol. If -no alignment is specified, @command{@value{AS}} will set the alignment to the +@ifset COFF-ELF +When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes +an optional third argument. This is the desired alignment of the symbol, +specified for ELF as a byte boundary (for example, an alignment of 16 means +that the least significant 4 bits of the address should be zero), and for PE +as a power of two (for example, an alignment of 5 means aligned to a 32-byte +boundary). The alignment must be an absolute expression, and it must be a +power of two. If @code{@value{LD}} allocates uninitialized memory for the +common symbol, it will use the alignment when placing the symbol. If no +alignment is specified, @command{@value{AS}} will set the alignment to the largest power of two less than or equal to the size of the symbol, up to a -maximum of 16. +maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This +is not the same as the executable image file alignment controlled by @code{@value{LD}}'s +@samp{--section-alignment} option; image file sections in PE are aligned to +multiples of 4096, which is far too large an alignment for ordinary variables. +It is rather the default alignment for (non-debug) sections within object +(@samp{*.o}) files, which are less strictly aligned.}. @end ifset @ifset HPPA |