gas: initialisation of expressionS in operand()

This patch removes clean_up_expression which runs just before operand()
returns.  clean_up_expression sets as yet uninitialised fields of
expressionS.  Well, it sets fields based on the value of X_op,
trusting that others have been written, and has one notable exception:
X_md is not initialised.

Instead initialise expressionS fully inside operand(), which is called
at the start of expr(), and introduce md_expr_init for the odd
backends that want to mess with X_md.

This is in response to an oss-fuzz report that read.c:pseudo_set calls
expr() leaving exp.X_md uninitialised and can copy that to a symbol
via symbol_set_value_expression.  tc-i386-intel.c:565 is one place
that later tests the uninitialised X_md.

	* config/tc-z80.h (md_expr_init, md_expr_init_rest): Define.
	* config/tc-microblaze.h: Likewise.
	* expr.c (clean_up_expression): Delete.
	(operand): Init expression early.
	(expr): Use md_expr_init_rest to init X_md when necessary.

0 files changed, 0 insertions, 0 deletions