-fpatchable-function-entry

Purpose

Generates an 8-word block before function entry and N-8 NOPs after function entry.

Syntax

Read syntax diagramSkip visual syntax diagram -fpatchable-function-entry =<N,8>

Default

None.

Parameters

N
N-8 is the number of NOPs to be generated.

Usage

In Clang, the -fpatchable-function-entry=<N,M> can be used to generate M NOPs before function entry and N-M NOPs after function entry. This option is available in IBM® Open XL C/C++ for AIX® 17.1.2. However, the IBM implementation of this option differs from the generic Clang functionality in the following ways:

  • M is required to be 8.
  • Instead of generating M NOPs before the function entry, an 8-word block is generated. This block contains 3.5 repetition of the hotpatch string, followed by an unconditional trap instruction to detect accidental branching to this area.
  • This functionality is available with the -ffunction-sections option starting from IBM Open XL C/C++ for AIX 17.1.2.2.

Predefined macros

None.

Related information

The "Clang command line argument reference" section in the Clang documentation