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expression.cc
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// expression.cc -- expressions in linker scripts for gold
// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <[email protected]>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#include "gold.h"
#include <string>
#include "elfcpp.h"
#include "parameters.h"
#include "symtab.h"
#include "layout.h"
#include "output.h"
#include "script.h"
#include "script-c.h"
namespace gold
{
// This file holds the code which handles linker expressions.
// The dot symbol, which linker scripts refer to simply as ".",
// requires special treatment. The dot symbol is set several times,
// section addresses will refer to it, output sections will change it,
// and it can be set based on the value of other symbols. We simplify
// the handling by prohibiting setting the dot symbol to the value of
// a non-absolute symbol.
// When evaluating the value of an expression, we pass in a pointer to
// this struct, so that the expression evaluation can find the
// information it needs.
struct Expression::Expression_eval_info
{
// The symbol table.
const Symbol_table* symtab;
// The layout--we use this to get section information.
const Layout* layout;
// Whether to check assertions.
bool check_assertions;
// Whether expressions can refer to the dot symbol. The dot symbol
// is only available within a SECTIONS clause.
bool is_dot_available;
// The current value of the dot symbol.
uint64_t dot_value;
// The section in which the dot symbol is defined; this is NULL if
// it is absolute.
Output_section* dot_section;
// Points to where the section of the result should be stored.
Output_section** result_section_pointer;
// Pointer to where the alignment of the result should be stored.
uint64_t* result_alignment_pointer;
};
// Evaluate an expression.
uint64_t
Expression::eval(const Symbol_table* symtab, const Layout* layout,
bool check_assertions)
{
return this->eval_maybe_dot(symtab, layout, check_assertions,
false, 0, NULL, NULL, NULL);
}
// Evaluate an expression which may refer to the dot symbol.
uint64_t
Expression::eval_with_dot(const Symbol_table* symtab, const Layout* layout,
bool check_assertions, uint64_t dot_value,
Output_section* dot_section,
Output_section** result_section_pointer,
uint64_t* result_alignment_pointer)
{
return this->eval_maybe_dot(symtab, layout, check_assertions, true,
dot_value, dot_section, result_section_pointer,
result_alignment_pointer);
}
// Evaluate an expression which may or may not refer to the dot
// symbol.
uint64_t
Expression::eval_maybe_dot(const Symbol_table* symtab, const Layout* layout,
bool check_assertions, bool is_dot_available,
uint64_t dot_value, Output_section* dot_section,
Output_section** result_section_pointer,
uint64_t* result_alignment_pointer)
{
Expression_eval_info eei;
eei.symtab = symtab;
eei.layout = layout;
eei.check_assertions = check_assertions;
eei.is_dot_available = is_dot_available;
eei.dot_value = dot_value;
eei.dot_section = dot_section;
// We assume the value is absolute, and only set this to a section
// if we find a section relative reference.
if (result_section_pointer != NULL)
*result_section_pointer = NULL;
eei.result_section_pointer = result_section_pointer;
eei.result_alignment_pointer = result_alignment_pointer;
return this->value(&eei);
}
// A number.
class Integer_expression : public Expression
{
public:
Integer_expression(uint64_t val)
: val_(val)
{ }
uint64_t
value(const Expression_eval_info*)
{ return this->val_; }
void
print(FILE* f) const
{ fprintf(f, "0x%llx", static_cast<unsigned long long>(this->val_)); }
private:
uint64_t val_;
};
extern "C" Expression*
script_exp_integer(uint64_t val)
{
return new Integer_expression(val);
}
// An expression whose value is the value of a symbol.
class Symbol_expression : public Expression
{
public:
Symbol_expression(const char* name, size_t length)
: name_(name, length)
{ }
uint64_t
value(const Expression_eval_info*);
void
print(FILE* f) const
{ fprintf(f, "%s", this->name_.c_str()); }
private:
std::string name_;
};
uint64_t
Symbol_expression::value(const Expression_eval_info* eei)
{
Symbol* sym = eei->symtab->lookup(this->name_.c_str());
if (sym == NULL || !sym->is_defined())
{
gold_error(_("undefined symbol '%s' referenced in expression"),
this->name_.c_str());
return 0;
}
if (eei->result_section_pointer != NULL)
*eei->result_section_pointer = sym->output_section();
if (parameters->target().get_size() == 32)
return eei->symtab->get_sized_symbol<32>(sym)->value();
else if (parameters->target().get_size() == 64)
return eei->symtab->get_sized_symbol<64>(sym)->value();
else
gold_unreachable();
}
// An expression whose value is the value of the special symbol ".".
// This is only valid within a SECTIONS clause.
class Dot_expression : public Expression
{
public:
Dot_expression()
{ }
uint64_t
value(const Expression_eval_info*);
void
print(FILE* f) const
{ fprintf(f, "."); }
};
uint64_t
Dot_expression::value(const Expression_eval_info* eei)
{
if (!eei->is_dot_available)
{
gold_error(_("invalid reference to dot symbol outside of "
"SECTIONS clause"));
return 0;
}
if (eei->result_section_pointer != NULL)
*eei->result_section_pointer = eei->dot_section;
return eei->dot_value;
}
// A string. This is either the name of a symbol, or ".".
extern "C" Expression*
script_exp_string(const char* name, size_t length)
{
if (length == 1 && name[0] == '.')
return new Dot_expression();
else
return new Symbol_expression(name, length);
}
// A unary expression.
class Unary_expression : public Expression
{
public:
Unary_expression(Expression* arg)
: arg_(arg)
{ }
~Unary_expression()
{ delete this->arg_; }
protected:
uint64_t
arg_value(const Expression_eval_info* eei,
Output_section** arg_section_pointer) const
{
return this->arg_->eval_maybe_dot(eei->symtab, eei->layout,
eei->check_assertions,
eei->is_dot_available,
eei->dot_value,
eei->dot_section,
arg_section_pointer,
eei->result_alignment_pointer);
}
void
arg_print(FILE* f) const
{ this->arg_->print(f); }
private:
Expression* arg_;
};
// Handle unary operators. We use a preprocessor macro as a hack to
// capture the C operator.
#define UNARY_EXPRESSION(NAME, OPERATOR) \
class Unary_ ## NAME : public Unary_expression \
{ \
public: \
Unary_ ## NAME(Expression* arg) \
: Unary_expression(arg) \
{ } \
\
uint64_t \
value(const Expression_eval_info* eei) \
{ \
Output_section* arg_section; \
uint64_t ret = OPERATOR this->arg_value(eei, &arg_section); \
if (arg_section != NULL && parameters->options().relocatable()) \
gold_warning(_("unary " #NAME " applied to section " \
"relative value")); \
return ret; \
} \
\
void \
print(FILE* f) const \
{ \
fprintf(f, "(%s ", #OPERATOR); \
this->arg_print(f); \
fprintf(f, ")"); \
} \
}; \
\
extern "C" Expression* \
script_exp_unary_ ## NAME(Expression* arg) \
{ \
return new Unary_ ## NAME(arg); \
}
UNARY_EXPRESSION(minus, -)
UNARY_EXPRESSION(logical_not, !)
UNARY_EXPRESSION(bitwise_not, ~)
// A binary expression.
class Binary_expression : public Expression
{
public:
Binary_expression(Expression* left, Expression* right)
: left_(left), right_(right)
{ }
~Binary_expression()
{
delete this->left_;
delete this->right_;
}
protected:
uint64_t
left_value(const Expression_eval_info* eei,
Output_section** section_pointer,
uint64_t* alignment_pointer) const
{
return this->left_->eval_maybe_dot(eei->symtab, eei->layout,
eei->check_assertions,
eei->is_dot_available,
eei->dot_value,
eei->dot_section,
section_pointer,
alignment_pointer);
}
uint64_t
right_value(const Expression_eval_info* eei,
Output_section** section_pointer,
uint64_t* alignment_pointer) const
{
return this->right_->eval_maybe_dot(eei->symtab, eei->layout,
eei->check_assertions,
eei->is_dot_available,
eei->dot_value,
eei->dot_section,
section_pointer,
alignment_pointer);
}
void
left_print(FILE* f) const
{ this->left_->print(f); }
void
right_print(FILE* f) const
{ this->right_->print(f); }
// This is a call to function FUNCTION_NAME. Print it. This is for
// debugging.
void
print_function(FILE* f, const char* function_name) const
{
fprintf(f, "%s(", function_name);
this->left_print(f);
fprintf(f, ", ");
this->right_print(f);
fprintf(f, ")");
}
private:
Expression* left_;
Expression* right_;
};
// Handle binary operators. We use a preprocessor macro as a hack to
// capture the C operator. KEEP_LEFT means that if the left operand
// is section relative and the right operand is not, the result uses
// the same section as the left operand. KEEP_RIGHT is the same with
// left and right swapped. IS_DIV means that we need to give an error
// if the right operand is zero. WARN means that we should warn if
// used on section relative values in a relocatable link. We always
// warn if used on values in different sections in a relocatable link.
#define BINARY_EXPRESSION(NAME, OPERATOR, KEEP_LEFT, KEEP_RIGHT, IS_DIV, WARN) \
class Binary_ ## NAME : public Binary_expression \
{ \
public: \
Binary_ ## NAME(Expression* left, Expression* right) \
: Binary_expression(left, right) \
{ } \
\
uint64_t \
value(const Expression_eval_info* eei) \
{ \
Output_section* left_section; \
uint64_t left_alignment = 0; \
uint64_t left = this->left_value(eei, &left_section, \
&left_alignment); \
Output_section* right_section; \
uint64_t right_alignment = 0; \
uint64_t right = this->right_value(eei, &right_section, \
&right_alignment); \
if (KEEP_RIGHT && left_section == NULL && right_section != NULL) \
{ \
if (eei->result_section_pointer != NULL) \
*eei->result_section_pointer = right_section; \
if (eei->result_alignment_pointer != NULL \
&& right_alignment > *eei->result_alignment_pointer) \
*eei->result_alignment_pointer = right_alignment; \
} \
else if (KEEP_LEFT \
&& left_section != NULL \
&& right_section == NULL) \
{ \
if (eei->result_section_pointer != NULL) \
*eei->result_section_pointer = left_section; \
if (eei->result_alignment_pointer != NULL \
&& left_alignment > *eei->result_alignment_pointer) \
*eei->result_alignment_pointer = left_alignment; \
} \
else if ((WARN || left_section != right_section) \
&& (left_section != NULL || right_section != NULL) \
&& parameters->options().relocatable()) \
gold_warning(_("binary " #NAME " applied to section " \
"relative value")); \
if (IS_DIV && right == 0) \
{ \
gold_error(_(#NAME " by zero")); \
return 0; \
} \
return left OPERATOR right; \
} \
\
void \
print(FILE* f) const \
{ \
fprintf(f, "("); \
this->left_print(f); \
fprintf(f, " %s ", #OPERATOR); \
this->right_print(f); \
fprintf(f, ")"); \
} \
}; \
\
extern "C" Expression* \
script_exp_binary_ ## NAME(Expression* left, Expression* right) \
{ \
return new Binary_ ## NAME(left, right); \
}
BINARY_EXPRESSION(mult, *, false, false, false, true)
BINARY_EXPRESSION(div, /, false, false, true, true)
BINARY_EXPRESSION(mod, %, false, false, true, true)
BINARY_EXPRESSION(add, +, true, true, false, true)
BINARY_EXPRESSION(sub, -, true, false, false, false)
BINARY_EXPRESSION(lshift, <<, false, false, false, true)
BINARY_EXPRESSION(rshift, >>, false, false, false, true)
BINARY_EXPRESSION(eq, ==, false, false, false, false)
BINARY_EXPRESSION(ne, !=, false, false, false, false)
BINARY_EXPRESSION(le, <=, false, false, false, false)
BINARY_EXPRESSION(ge, >=, false, false, false, false)
BINARY_EXPRESSION(lt, <, false, false, false, false)
BINARY_EXPRESSION(gt, >, false, false, false, false)
BINARY_EXPRESSION(bitwise_and, &, true, true, false, true)
BINARY_EXPRESSION(bitwise_xor, ^, true, true, false, true)
BINARY_EXPRESSION(bitwise_or, |, true, true, false, true)
BINARY_EXPRESSION(logical_and, &&, false, false, false, true)
BINARY_EXPRESSION(logical_or, ||, false, false, false, true)
// A trinary expression.
class Trinary_expression : public Expression
{
public:
Trinary_expression(Expression* arg1, Expression* arg2, Expression* arg3)
: arg1_(arg1), arg2_(arg2), arg3_(arg3)
{ }
~Trinary_expression()
{
delete this->arg1_;
delete this->arg2_;
delete this->arg3_;
}
protected:
uint64_t
arg1_value(const Expression_eval_info* eei,
Output_section** section_pointer) const
{
return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
eei->check_assertions,
eei->is_dot_available,
eei->dot_value,
eei->dot_section,
section_pointer,
NULL);
}
uint64_t
arg2_value(const Expression_eval_info* eei,
Output_section** section_pointer,
uint64_t* alignment_pointer) const
{
return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
eei->check_assertions,
eei->is_dot_available,
eei->dot_value,
eei->dot_section,
section_pointer,
alignment_pointer);
}
uint64_t
arg3_value(const Expression_eval_info* eei,
Output_section** section_pointer,
uint64_t* alignment_pointer) const
{
return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
eei->check_assertions,
eei->is_dot_available,
eei->dot_value,
eei->dot_section,
section_pointer,
alignment_pointer);
}
void
arg1_print(FILE* f) const
{ this->arg1_->print(f); }
void
arg2_print(FILE* f) const
{ this->arg2_->print(f); }
void
arg3_print(FILE* f) const
{ this->arg3_->print(f); }
private:
Expression* arg1_;
Expression* arg2_;
Expression* arg3_;
};
// The conditional operator.
class Trinary_cond : public Trinary_expression
{
public:
Trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
: Trinary_expression(arg1, arg2, arg3)
{ }
uint64_t
value(const Expression_eval_info* eei)
{
Output_section* arg1_section;
uint64_t arg1 = this->arg1_value(eei, &arg1_section);
return (arg1
? this->arg2_value(eei, eei->result_section_pointer,
eei->result_alignment_pointer)
: this->arg3_value(eei, eei->result_section_pointer,
eei->result_alignment_pointer));
}
void
print(FILE* f) const
{
fprintf(f, "(");
this->arg1_print(f);
fprintf(f, " ? ");
this->arg2_print(f);
fprintf(f, " : ");
this->arg3_print(f);
fprintf(f, ")");
}
};
extern "C" Expression*
script_exp_trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
{
return new Trinary_cond(arg1, arg2, arg3);
}
// Max function.
class Max_expression : public Binary_expression
{
public:
Max_expression(Expression* left, Expression* right)
: Binary_expression(left, right)
{ }
uint64_t
value(const Expression_eval_info* eei)
{
Output_section* left_section;
uint64_t left_alignment;
uint64_t left = this->left_value(eei, &left_section, &left_alignment);
Output_section* right_section;
uint64_t right_alignment;
uint64_t right = this->right_value(eei, &right_section, &right_alignment);
if (left_section == right_section)
{
if (eei->result_section_pointer != NULL)
*eei->result_section_pointer = left_section;
}
else if ((left_section != NULL || right_section != NULL)
&& parameters->options().relocatable())
gold_warning(_("max applied to section relative value"));
if (eei->result_alignment_pointer != NULL)
{
uint64_t ra = *eei->result_alignment_pointer;
if (left > right)
ra = std::max(ra, left_alignment);
else if (right > left)
ra = std::max(ra, right_alignment);
else
ra = std::max(ra, std::max(left_alignment, right_alignment));
*eei->result_alignment_pointer = ra;
}
return std::max(left, right);
}
void
print(FILE* f) const
{ this->print_function(f, "MAX"); }
};
extern "C" Expression*
script_exp_function_max(Expression* left, Expression* right)
{
return new Max_expression(left, right);
}
// Min function.
class Min_expression : public Binary_expression
{
public:
Min_expression(Expression* left, Expression* right)
: Binary_expression(left, right)
{ }
uint64_t
value(const Expression_eval_info* eei)
{
Output_section* left_section;
uint64_t left_alignment;
uint64_t left = this->left_value(eei, &left_section, &left_alignment);
Output_section* right_section;
uint64_t right_alignment;
uint64_t right = this->right_value(eei, &right_section, &right_alignment);
if (left_section == right_section)
{
if (eei->result_section_pointer != NULL)
*eei->result_section_pointer = left_section;
}
else if ((left_section != NULL || right_section != NULL)
&& parameters->options().relocatable())
gold_warning(_("min applied to section relative value"));
if (eei->result_alignment_pointer != NULL)
{
uint64_t ra = *eei->result_alignment_pointer;
if (left < right)
ra = std::max(ra, left_alignment);
else if (right < left)
ra = std::max(ra, right_alignment);
else
ra = std::max(ra, std::max(left_alignment, right_alignment));
*eei->result_alignment_pointer = ra;
}
return std::min(left, right);
}
void
print(FILE* f) const
{ this->print_function(f, "MIN"); }
};
extern "C" Expression*
script_exp_function_min(Expression* left, Expression* right)
{
return new Min_expression(left, right);
}
// Class Section_expression. This is a parent class used for
// functions which take the name of an output section.
class Section_expression : public Expression
{
public:
Section_expression(const char* section_name, size_t section_name_len)
: section_name_(section_name, section_name_len)
{ }
uint64_t
value(const Expression_eval_info*);
void
print(FILE* f) const
{ fprintf(f, "%s(%s)", this->function_name(), this->section_name_.c_str()); }
protected:
// The child class must implement this.
virtual uint64_t
value_from_output_section(const Expression_eval_info*,
Output_section*) = 0;
// The child class must implement this.
virtual uint64_t
value_from_script_output_section(uint64_t address, uint64_t load_address,
uint64_t addralign, uint64_t size) = 0;
// The child class must implement this.
virtual const char*
function_name() const = 0;
private:
std::string section_name_;
};
uint64_t
Section_expression::value(const Expression_eval_info* eei)
{
const char* section_name = this->section_name_.c_str();
Output_section* os = eei->layout->find_output_section(section_name);
if (os != NULL)
return this->value_from_output_section(eei, os);
uint64_t address;
uint64_t load_address;
uint64_t addralign;
uint64_t size;
const Script_options* ss = eei->layout->script_options();
if (ss->saw_sections_clause())
{
if (ss->script_sections()->get_output_section_info(section_name,
&address,
&load_address,
&addralign,
&size))
return this->value_from_script_output_section(address, load_address,
addralign, size);
}
gold_error("%s called on nonexistent output section '%s'",
this->function_name(), section_name);
return 0;
}
// ABSOLUTE function.
class Absolute_expression : public Unary_expression
{
public:
Absolute_expression(Expression* arg)
: Unary_expression(arg)
{ }
uint64_t
value(const Expression_eval_info* eei)
{
uint64_t ret = this->arg_value(eei, NULL);
// Force the value to be absolute.
if (eei->result_section_pointer != NULL)
*eei->result_section_pointer = NULL;
return ret;
}
void
print(FILE* f) const
{
fprintf(f, "ABSOLUTE(");
this->arg_print(f);
fprintf(f, ")");
}
};
extern "C" Expression*
script_exp_function_absolute(Expression* arg)
{
return new Absolute_expression(arg);
}
// ALIGN function.
class Align_expression : public Binary_expression
{
public:
Align_expression(Expression* left, Expression* right)
: Binary_expression(left, right)
{ }
uint64_t
value(const Expression_eval_info* eei)
{
Output_section* align_section;
uint64_t align = this->right_value(eei, &align_section, NULL);
if (align_section != NULL
&& parameters->options().relocatable())
gold_warning(_("aligning to section relative value"));
if (eei->result_alignment_pointer != NULL
&& align > *eei->result_alignment_pointer)
{
uint64_t a = align;
while ((a & (a - 1)) != 0)
a &= a - 1;
*eei->result_alignment_pointer = a;
}
uint64_t value = this->left_value(eei, eei->result_section_pointer, NULL);
if (align <= 1)
return value;
return ((value + align - 1) / align) * align;
}
void
print(FILE* f) const
{ this->print_function(f, "ALIGN"); }
};
extern "C" Expression*
script_exp_function_align(Expression* left, Expression* right)
{
return new Align_expression(left, right);
}
// ASSERT function.
class Assert_expression : public Unary_expression
{
public:
Assert_expression(Expression* arg, const char* message, size_t length)
: Unary_expression(arg), message_(message, length)
{ }
uint64_t
value(const Expression_eval_info* eei)
{
uint64_t value = this->arg_value(eei, eei->result_section_pointer);
if (!value && eei->check_assertions)
gold_error("%s", this->message_.c_str());
return value;
}
void
print(FILE* f) const
{
fprintf(f, "ASSERT(");
this->arg_print(f);
fprintf(f, ", %s)", this->message_.c_str());
}
private:
std::string message_;
};
extern "C" Expression*
script_exp_function_assert(Expression* expr, const char* message,
size_t length)
{
return new Assert_expression(expr, message, length);
}
// ADDR function.
class Addr_expression : public Section_expression
{
public:
Addr_expression(const char* section_name, size_t section_name_len)
: Section_expression(section_name, section_name_len)
{ }
protected:
uint64_t
value_from_output_section(const Expression_eval_info* eei,
Output_section* os)
{
if (eei->result_section_pointer != NULL)
*eei->result_section_pointer = os;
return os->address();
}
uint64_t
value_from_script_output_section(uint64_t address, uint64_t, uint64_t,
uint64_t)
{ return address; }
const char*
function_name() const
{ return "ADDR"; }
};
extern "C" Expression*
script_exp_function_addr(const char* section_name, size_t section_name_len)
{
return new Addr_expression(section_name, section_name_len);
}
// ALIGNOF.
class Alignof_expression : public Section_expression
{
public:
Alignof_expression(const char* section_name, size_t section_name_len)
: Section_expression(section_name, section_name_len)
{ }
protected:
uint64_t
value_from_output_section(const Expression_eval_info*,
Output_section* os)
{ return os->addralign(); }
uint64_t
value_from_script_output_section(uint64_t, uint64_t, uint64_t addralign,
uint64_t)
{ return addralign; }
const char*
function_name() const
{ return "ALIGNOF"; }
};
extern "C" Expression*
script_exp_function_alignof(const char* section_name, size_t section_name_len)
{
return new Alignof_expression(section_name, section_name_len);
}
// CONSTANT. It would be nice if we could simply evaluate this
// immediately and return an Integer_expression, but unfortunately we
// don't know the target.
class Constant_expression : public Expression
{
public:
Constant_expression(const char* name, size_t length);
uint64_t
value(const Expression_eval_info*);
void
print(FILE* f) const;
private:
enum Constant_function
{
CONSTANT_MAXPAGESIZE,
CONSTANT_COMMONPAGESIZE
};
Constant_function function_;
};
Constant_expression::Constant_expression(const char* name, size_t length)
{
if (length == 11 && strncmp(name, "MAXPAGESIZE", length) == 0)
this->function_ = CONSTANT_MAXPAGESIZE;
else if (length == 14 && strncmp(name, "COMMONPAGESIZE", length) == 0)
this->function_ = CONSTANT_COMMONPAGESIZE;
else
{
std::string s(name, length);
gold_error(_("unknown constant %s"), s.c_str());
this->function_ = CONSTANT_MAXPAGESIZE;
}
}
uint64_t
Constant_expression::value(const Expression_eval_info*)
{
switch (this->function_)
{
case CONSTANT_MAXPAGESIZE:
return parameters->target().abi_pagesize();
case CONSTANT_COMMONPAGESIZE:
return parameters->target().common_pagesize();
default:
gold_unreachable();
}
}
void
Constant_expression::print(FILE* f) const
{
const char* name;
switch (this->function_)
{
case CONSTANT_MAXPAGESIZE:
name = "MAXPAGESIZE";