365 lines
12 KiB
Text
Executable file
365 lines
12 KiB
Text
Executable file
.de NS
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.sp
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.in 0
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\\fBANS \\$1:\\fP
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..
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.TL
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Amsterdam Compiler Kit-ANSI C compiler compliance statements
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.AU
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Hans van Eck
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.AI
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Dept. of Mathematics and Computer Science
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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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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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.FS
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\(dg when cross-compiling, run-time behaviour may be different from
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compile-time behaviour
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.FE
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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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following specification:
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.br
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"<file>", line <nr>: [(<class>)] <diagnostic>
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.br
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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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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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.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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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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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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The compiler assumes ASCII-characters in both the source and execution
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character set.
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.IP -
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There are no multi-byte characters.
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.IP -
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There 8 bits in a character.
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.IP -
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Character constants with values that can not be represented in 8 bits
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are truncated.
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.IP -
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Character constants that are more than 1 character wide will have the
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first character specified in the least significant byte.
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.IP -
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The only supported locale is "C".
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.IP -
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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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.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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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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expected on a 2-complement machine.
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.IP -
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If either operand is negative, whether the result of the / operator is the
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largest integer less than or equal to the algebraic quotient or the
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smallest integer greater than or equal to the algebraic quotient is machine
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dependent, as is the sign of the result of the % operator.
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.IP -
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The right-shift of a negative value is negative.
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.NS A.6.3.6
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.IP -
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The representation of floating-point values is machine-dependent.
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When native floating-point is not present an IEEE-emulation is used.
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The compiler uses high-precision floating-point for constant folding.
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.IP -
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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 (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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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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.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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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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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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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 field with a size of 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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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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constitutes an access.
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.S A.6.3.11
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.IP -
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There is no fixed limit on the number of declarators that may modify an
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arithmetic, structure or union type, although specifying too many may
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cause the compiler to run out of memory.
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.NS A.6.3.12
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.IP -
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The maximum number of cases in a switch-statement is in the order of
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1e9, although the compiler may run out of memory somewhat earlier.
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.NS A.6.3.13
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.IP -
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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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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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/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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which does the include resides.
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.IP -
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The characters in a h- or q- char-sequence are taken to be UNIX
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paths.
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.IP -
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Neither the compiler nor the preprocessor know any pragmas.
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.IP -
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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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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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.ti +4n
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"Assertion "<expr>" failed, file "<file>", line <line>",
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.br
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where <expr> is the argument to the assert macro, printed as string.
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(the <file> and <line> should be clear)
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.KS
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.IP -
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The sets for character test macros.
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.TS
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l l.
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name: set:
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isalnum() 0-9A-Za-z
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isalpha() A-Za-z
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iscntrl() \e000-\e037\e177
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islower() a-z
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isupper() A-Z
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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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characters.
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.KS
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.IP -
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The behaviour of mathematic functions on domain error:
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.TS
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l c
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l n.
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name: returns:
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asin() 0.0
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acos() 0.0
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atan2() 0.0
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fmod() 0.0
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log() -HUGE_VAL
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log10() -HUGE_VAL
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pow() 0.0
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sqrt() 0.0
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.TE
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.KE
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.IP -
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Underflow range errors do not cause errno to be set.
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.IP -
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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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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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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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.IP -
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White space characters before a new-line appear when read in.
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.IP -
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There may be any number of null characters appended to a binary
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stream.
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.IP -
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The file position indicator of an append mode stream is initially
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positioned at the beginning of the file.
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.IP -
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A write on a text stream does not cause the associated file to be
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truncated beyond that point.
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.IP -
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The buffering intended by the standard is fully supported.
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.IP -
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A zero-length file actually exists.
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.IP -
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A file name can consist of any character, except for the '\e0' and
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the '/'.
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.IP -
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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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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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.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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.IP -
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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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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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The value of errno when fgetpos() or ftell() failed is that of lseek().
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This means:
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.RS
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.IP "EBADF \-" 10
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when the stream is not valid
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.IP "ESPIPE \-"
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when fildes is associated with a pipe (and on some systems: sockets)
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.IP "EINVAL \-"
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the resulting file pointer would be negative
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.RE
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.LP
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.IP -
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The messages generated by perror() depend on the value of errno.
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The mapping of errors to strings is done by strerror().
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.IP -
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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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(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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The exit() function returns the low-order eight bits of its argument
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to the environment.
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.IP -
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The predefined environment names are controlled by the user.
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Setting environment variables is done through the putenv() function.
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This function accepts a pointer to char as its argument.
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To set f.i. the environment variable TERM to a230 one writes
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.ti +4n
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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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0 otherwise.
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.LP
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.IP -
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The argument to system is passed as argument to /bin/sh -c.
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.IP -
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The strings returned by strerror() depend on errno in the following
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way:
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.TS
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l l.
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errno string
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0 "Error 0",
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EPERM "Not owner",
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ENOENT "No such file or directory",
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ESRCH "No such process",
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EINTR "Interrupted system call",
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EIO "I/O error",
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ENXIO "No such device or address",
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E2BIG "Arg list too long",
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ENOEXEC "Exec format error",
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EBADF "Bad file number",
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ECHILD "No children",
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EAGAIN "No more processes",
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ENOMEM "Not enough core",
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EACCES "Permission denied",
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EFAULT "Bad address",
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ENOTBLK "Block device required",
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EBUSY "Mount device busy",
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EEXIST "File exists",
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EXDEV "Cross-device link",
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ENODEV "No such device",
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ENOTDIR "Not a directory",
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EISDIR "Is a directory",
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EINVAL "Invalid argument",
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ENFILE "File table overflow",
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EMFILE "Too many open files",
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ENOTTY "Not a typewriter",
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ETXTBSY "Text file busy",
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EFBUG "File too large",
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ENOSPC "No space left on device",
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ESPIPE "Illegal seek",
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EROFS "Read-only file system",
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EMLINK "Too many links",
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EPIPE "Broken pipe",
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EDOM "Math argument",
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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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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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The clock() function returns the number of ticks since process
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startup.
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.SH
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References
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.IP [1]
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ANS X3.159-1989
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.I
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American National Standard for Information Systems -
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Programming Language C
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.R
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