added top element size computation information
This commit is contained in:
eck
@@ -13,7 +13,7 @@ Vrije Universiteit
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Amsterdam, The Netherlands
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.PP
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This document specifies the implementation-defined behaviour of the ANSI-C
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front end of the Amsterdam Compiler Kit as required by ANS X3.159-1989. Since
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front end of the Amsterdam Compiler Kit as required by ANS X3.159-1989. Since
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the implementation-defined behaviour sometimes depends on the machine
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compiling on or for, some items will be left unspecified in this
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document\(dg.
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@@ -24,7 +24,7 @@ compile-time behaviour
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The compiler assumes that it runs on a UNIX system.
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.NS A.6.3.1
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.IP -
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Diagnostics are placed on the standard error output. They have the
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Diagnostics are placed on the standard error output. They have the
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following specification:
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.br
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"<file>", line <nr>: [(<class>)] <diagnostic>
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@@ -33,21 +33,21 @@ There are three classes of diagnostics: "error", "strict" and "warning".
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When the class is "error", the <class> is absent.
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.br
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The class "strict" is used for violations of the standard which are
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not severe enough to stop compilation. An example is the the occurrence
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not severe enough to stop compilation. An example is the the occurrence
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of non white-space after an '#else' or '#endif' pre-processing
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directive. The class "warning" is used for legal but dubious
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constructions. An example is overflow of constant expressions.
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directive. The class "warning" is used for legal but dubious
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constructions. An example is overflow of constant expressions.
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.NS A.6.3.2
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.IP -
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The function 'main' can have two arguments. The first argument is an
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integer specifying the number of arguments on the command line. The second
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The function 'main' can have two arguments. The first argument is an
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integer specifying the number of arguments on the command line. The second
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argument is a pointer to an array of pointers to the arguments (as
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strings).
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.IP -
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Interactive devices are terminals.
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.NS A.6.3.3
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.IP -
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The number of significant characters is an option. By default it is 64.
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The number of significant characters is an option. By default it is 64.
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There is a distinction between upper and lower case.
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.NS A.6.3.4
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.IP -
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@@ -70,13 +70,13 @@ A plain 'char' has the same range of values as 'signed char'.
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.NS A.6.3.5
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.IP -
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The compiler assumes that it works on and compiles for a
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2-complement binary-number system. Shorts will use 2 bytes and longs
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will use 4 bytes. The size of integers are machine dependent.
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2-complement binary-number system. Shorts will use 2 bytes and longs
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will use 4 bytes. The size of integers are machine dependent.
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.IP -
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Converting an integer to a shorter signed integer is implemented by
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ignoring the high-order byte(s) of the former.
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Converting a unsigned integer to a signed integer of the same type is
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only done in administration. This means that the bit-pattern remains
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only done in administration. This means that the bit-pattern remains
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unchanged.
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.IP -
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The result of bitwise operations on signed integers are what can be
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@@ -98,45 +98,45 @@ Truncation is always to the nearest floating-point number that can
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be represented.
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.NS A.6.3.7
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.IP -
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The type returned by the sizeof-operator is 'unsigned int'. This is done
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for backward compatibility reasons.
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The type returned by the sizeof-operator (also known as size_t)
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is 'unsigned int'. This is done for backward compatibility reasons.
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.IP -
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Casting an integer to a pointer or vice versa has no effect in
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bit-pattern when the sizes are equal. Otherwise the value will be
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bit-pattern when the sizes are equal. Otherwise the value will be
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truncated or zero-extended (depending on the direction of the
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conversion and the relative sizes).
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.IP -
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When a pointer is as large as an integer, the type of a 'ptrdiff_t' will
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be 'int'. Otherwise the type will be 'long'.
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be 'int'. Otherwise the type will be 'long'.
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.NS A.6.3.8
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.IP -
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Since the front end has only limited control over the registers, it can
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only make it more likely that variables that are declared as
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registers also end up in registers. The only things that can possibly be
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registers also end up in registers. The only things that can possibly be
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put into registers are : 'int', 'long', 'float', 'double', 'long double'
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and pointers.
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.NS A.6.3.9
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.IP -
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When a member of a union object is accessed using a member of a
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different type, the resulting value will usually be garbage. The
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different type, the resulting value will usually be garbage. The
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compiler makes no effort to catch these errors.
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.IP -
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The alignment of types is a compile-time option. The alignment of
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a structure-member is the alignment of its type. Usually, the
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alignment is passed on to the compiler by the 'ack' program. When a
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The alignment of types is a compile-time option. The alignment of
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a structure-member is the alignment of its type. Usually, the
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alignment is passed on to the compiler by the 'ack' program. When a
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user wants to do this manually, he/she should be prepared for trouble.
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.IP -
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A "plain" 'int' bit-field is taken as a 'signed int'. This means that
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A "plain" 'int' bit-field is taken as a 'signed int'. This means that
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a field with a size 1 bit can only store the values 0 and -1.
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.IP -
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The order of allocation of bit-fields is a compile-time option. By
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The order of allocation of bit-fields is a compile-time option. By
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default, high-order bits are allocated first.
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.IP -
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An enum has the same size as a "plain" 'int'.
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.NS A.6.3.10
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.IP -
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An access to a volatile declared variable is done by just mentioning
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the variable. E.g. the statement "x;" where x is declared volatile,
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the variable. E.g. the statement "x;" where x is declared volatile,
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constitutes an access.
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.S A.6.3.11
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.IP -
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@@ -153,10 +153,10 @@ Since both the pre-processor and the compiler assume ASCII-characters,
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a single character constant in a conditional-inclusion directive
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matches the same value in the execution character set.
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.IP -
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The pre-processor recognizes -I... command-line options. The
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directories thus specified are searched first. After that, depending on the
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The pre-processor recognizes -I... command-line options. The
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directories thus specified are searched first. After that, depending on the
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command that the preprocessor is called with, machine/system-dependant
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directories are searched. After that, ~em/include/_tail_ac and
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directories are searched. After that, ~em/include/_tail_ac and
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/usr/include are visited.
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.IP -
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Quoted names are first looked for in the directory in which the file
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@@ -171,7 +171,7 @@ Since the compiler runs on UNIX, __DATE__ and __TIME__ will always be
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defined.
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.NS A.6.3.14
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.IP -
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NULL is defined as ((void *)0). This in order to flag dubious
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NULL is defined as ((void *)0). This in order to flag dubious
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constructions like "int x = NULL;".
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.IP -
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The diagnostic printed by 'assert' is as follows:
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@@ -195,7 +195,7 @@ isprint() <space>-~ (== \e040-\e176)
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.TE
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.KE
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As an addition, there is an isascii() macro, which tests whether a character
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is an ascii character. Characters in the range from \e000 to \e177 are ascii
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is an ascii character. Characters in the range from \e000 to \e177 are ascii
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characters.
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.KS
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.IP -
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@@ -221,9 +221,9 @@ The function fmod() returns 0.0 and sets errno to EDOM when the second
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argument is 0.0.
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.IP -
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The set of signals for the signal() function depends on the UNIX-system
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which the compiler is compiling for. The default handling, semantics
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which the compiler is compiling for. The default handling, semantics
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and behaviour of these signals are those specified by the operating
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system vendor. The default handling is not reset when SIGILL is
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system vendor. The default handling is not reset when SIGILL is
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received.
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.IP -
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A text-stream need not end in a new-line character.
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@@ -249,11 +249,11 @@ the '/'.
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A file can be open multiple times.
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.IP -
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When a remove() is done on an open file, reading and writing behave
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just as can be expected from a non-removed file. When the associated
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just as can be expected from a non-removed file. When the associated
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stream is closed, all written data will be lost.
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.IP -
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When a file exists prior to a call to rename(), the behaviour is that
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of the underlying UNIX system. Normally, the call would fail.
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of the underlying UNIX system. Normally, the call would fail.
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.IP -
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The %p conversion in fprintf() has the same effect as %#x or %#lx,
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depending on the sizes of pointer and integer.
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@@ -262,7 +262,7 @@ The %p conversion in fscanf() has the same effect as %x or %lx,
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depending on the sizes of pointer and integer.
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.IP -
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A - character that is neither the first nor the last character in the
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scanlist for %[ conversion is taken to be a range indicator. When the
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scanlist for %[ conversion is taken to be a range indicator. When the
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first character has a higher ASCII-value than the second, the - will
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just be put into the scanlist.
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.IP -
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@@ -284,7 +284,7 @@ The mapping of errors to strings is done by strerror().
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When the requested size is zero, malloc(), calloc() and realloc()
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return a null-pointer.
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.IP -
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When abort() is called, output buffers will be flushed. Temporary files
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When abort() is called, output buffers will be flushed. Temporary files
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(made with the tmpfile() function) will have disappeared when SIGABRT
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is not caught or ignored.
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.IP -
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@@ -300,7 +300,7 @@ putenv("TERM=a230");
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.br
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The argument to putenv() is stored in an internal table, so malloc'ed
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strings can not be freed until another call to putenv() (which sets the
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same environment variable) is made. The function returns 1 if it fails,
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same environment variable) is made. The function returns 1 if it fails,
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0 otherwise.
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.LP
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.IP -
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@@ -349,7 +349,7 @@ ERANGE "Result too large"
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.TE
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everything else causes strerror() to return "unknown error"
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.IP -
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The local time zone is per default MET (GMT + 1:00:00). This can be
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The local time zone is per default MET (GMT + 1:00:00). This can be
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changed through the TZ environment variable, or by some changes in the
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sources.
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.IP -
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