| Copyright © 1997, 1998 ARM Limited. All rights reserved. | ARM DUI 0041C |
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The precise attributes of a C library are specific to a particular implementation of it. The generic ARM C library has or supports the following features:
The macro NULL expands
to the integer constant 0.
If a program redefines a reserved external identifier, an error may occur when the program is linked with the standard libraries. If it is not linked with standard libraries, no error will be detected.
The assert() function prints
the following message and then calls the abort() function:
*** assertion failed: expression, file filename, line linenumber
The following functions usually test only for characters whose values are in the range 0 to 127 (inclusive):
isalnum()
isalpha()
iscntrl()
islower()
isprint()
isupper()
ispunct()
Characters with values greater than 127 return a result of
0 for all these functions except iscntrl() which
returns non-zero for 0 to 31, and 128 to 255.
After the call setlocale(LC_CTYPE, "ISO8859-1"), the
statements in Table 3.4 apply
to character codes and affect the results returned by the ctype() functions:
The mathematical functions return the values in Table 3.5.
Table 3.5. Mathematical functions
| Function | Condition | Returned value |
|---|---|---|
log(x) | x <= 0 | –HUGE_VAL |
log10(x) | x <= 0 | –HUGE_VAL |
sqrt(x) | x < 0 | –HUGE_VAL |
atan2(x,y) | x = y = 0 | –HUGE_VAL |
asin(x) | abs(x) > 1 |
|
acos(x) | abs(x) > 1 |
|
pow(x,y) | x=y=0 |
|
Where –HUGE_VAL is returned, a number is
returned which is defined in the header math.h.
Consult the errno variable for the error number.
The mathematical functions set errno to ERANGE on
underflow range errors.
A domain error occurs if the second argument of fmod() is
zero, and –HUGE_VAL is returned.
The set of signals for the generic signal() function
shown in Table 3.6.
Table 3.6. Signal function signals
| Signal | Description |
|---|---|
SIGABRT | abort |
SIGFPE | arithmetic exception |
SIGILL | illegal instruction |
SIGINT | attention request from user |
SIGSEGV | bad memory access |
SIGTERM | termination request |
SIGSTAK | stack overflow |
The default handling of all recognized signals is to print
a diagnostic message and call exit(). This
default behavior applies at program startup.
When a signal occurs, if func points to
a function, the equivalent of signal(sig, SIG_DFL) is
first executed. If the SIGILL signal is received
by a handler specified to the signal() function,
the default handling is reset.
The generic ARM C library also has the following characteristics relating to I/O. Note that a given targeting of the ARM C library may not have the same characteristics:
The last line of a text stream does not require a terminating newline character.
Space characters written out to a text stream immediately before a newline character do appear when read back in.
No null characters are appended to a binary output stream.
The file position indicator of an append mode stream is initially placed at the end of the file.
A write to a text stream does not cause the associated file to be truncated beyond that point (device dependent).
The characteristics of file buffering are as intended
by section 4.9.3 of the ANSI C standard. The maximum number of open
files is set in stdio.h as:
#define _SYS_OPEN 16
if Angel is in use.
A zero-length file (in which no characters have been written by an output stream) does exist.
The same file can be opened many times for reading, but only once for writing or updating. A file cannot be open simultaneously for reading on one stream and for writing or updating on another.
Local time zones and Daylight Saving Time are not implemented. The values returned will always indicate that the information is not available.
The status returned by exit() is
the same value that was passed to it. For definitions of EXIT_SUCCESS and EXIT_FAILURE,
refer to the header file stdlib.h.
The error messages returned by the strerror() function
are identical to those given by the perror() function.
If the size of area requested is zero, calloc(), malloc() and realloc() return NULL.
abort() closes all open files,
and deletes all temporary files.
fprintf() prints %p arguments
in hexadecimal format (lowercase) as if a precision of 8 had been
specified. If the variant form (%#p) is used,
the number is preceded by the character @.
fscanf() treats %p arguments
identically to %x arguments.
fscanf() always treats the
character "-" in a %...[...] argument as a literal character.
ftell() and fgetpos() set errno to
the value of EDOM on failure.
perror() generates the messages
in Table 3.7.
The following characteristics, required to be specified in an ANSI-compliant implementation, are unspecified in the generic ARM C library:
the validity of a filename
whether remove() can remove
an open file
the effect of calling the rename() function
when the new name already exists
the effect of calling getenv() (the
default is to return NULL, no value available)
the effect of calling system()
the value returned by clock().
| Copyright © 1997, 1998 ARM Limited. All rights reserved. | ARM DUI 0041C |
| PDF version | |
| Home > ARM Compiler Reference > Standard C implementation definition > Library functions |