Resolve Issue: coder.inline("never") and coder.nonInlineCall Do Not Prevent Function Inlining

Issue

In certain cases, the code generator inlines a MATLAB^® function, replacing the function call with a constant value, even though you call the function using coder.nonInlineCall or you include the coder.inline("never") directive in the function body.

For example, create a function test_inline that calls local function local with a constant input. Instruct the code generator not to inline local by using the coder.inline("never") directive.

function y = test_inline()
x = local(0);
if(x == 0)
    y = 0;
else 
    y = 1;
end
end

function y = local(x)
coder.inline("never");
y = x;
end

Generate C code for test_inline and inspect the entry-point function in the generated code. The code generator inlines local, replacing the function call with a constant value, even though the MATLAB definition contains the coder.inline("never") directive.

double test_inline(void)
{
  return 0.0;
}

Possible Solutions

To prevent the code generator from inlining a function, use coder.ignoreConst on one of the inputs at the function call site in your MATLAB code. The coder.ignoreConst function prevents the code generator from returning the function output as a constant value.

Modify test_inline to instruct the code generator to call coder.ignoreConst on the input to local.

function y = test_inline()
x = local(coder.ignoreConst(0));
if(x == 0)
    y = 0;
else 
    y = 1;
end
end

function y = local(x)
coder.inline("never");
y = x;
end

Generate C code for test_inline and inspect the entry-point function in the generated code. The code generator does not inline local.

static double local(void)
{
  return 0.0;
}
double test_inline(void)
{
  return !(local() == 0.0);
}