diff gcc/gcov-io.h @ 0:a06113de4d67

first commit
author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
parents
children 77e2b8dfacca
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/gcov-io.h	Fri Jul 17 14:47:48 2009 +0900
@@ -0,0 +1,614 @@
+/* File format for coverage information
+   Copyright (C) 1996, 1997, 1998, 2000, 2002,
+   2003, 2004, 2005, 2008, 2009 Free Software Foundation, Inc.
+   Contributed by Bob Manson <manson@cygnus.com>.
+   Completely remangled by Nathan Sidwell <nathan@codesourcery.com>.
+
+This file is part of GCC.
+
+GCC 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, or (at your option) any later
+version.
+
+GCC 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.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+
+/* Coverage information is held in two files.  A notes file, which is
+   generated by the compiler, and a data file, which is generated by
+   the program under test.  Both files use a similar structure.  We do
+   not attempt to make these files backwards compatible with previous
+   versions, as you only need coverage information when developing a
+   program.  We do hold version information, so that mismatches can be
+   detected, and we use a format that allows tools to skip information
+   they do not understand or are not interested in.
+
+   Numbers are recorded in the 32 bit unsigned binary form of the
+   endianness of the machine generating the file. 64 bit numbers are
+   stored as two 32 bit numbers, the low part first.  Strings are
+   padded with 1 to 4 NUL bytes, to bring the length up to a multiple
+   of 4. The number of 4 bytes is stored, followed by the padded
+   string. Zero length and NULL strings are simply stored as a length
+   of zero (they have no trailing NUL or padding).
+
+   	int32:  byte3 byte2 byte1 byte0 | byte0 byte1 byte2 byte3
+	int64:  int32:low int32:high
+	string: int32:0 | int32:length char* char:0 padding
+	padding: | char:0 | char:0 char:0 | char:0 char:0 char:0
+	item: int32 | int64 | string
+
+   The basic format of the files is
+
+   	file : int32:magic int32:version int32:stamp record*
+
+   The magic ident is different for the notes and the data files.  The
+   magic ident is used to determine the endianness of the file, when
+   reading.  The version is the same for both files and is derived
+   from gcc's version number. The stamp value is used to synchronize
+   note and data files and to synchronize merging within a data
+   file. It need not be an absolute time stamp, merely a ticker that
+   increments fast enough and cycles slow enough to distinguish
+   different compile/run/compile cycles.
+   
+   Although the ident and version are formally 32 bit numbers, they
+   are derived from 4 character ASCII strings.  The version number
+   consists of the single character major version number, a two
+   character minor version number (leading zero for versions less than
+   10), and a single character indicating the status of the release.
+   That will be 'e' experimental, 'p' prerelease and 'r' for release.
+   Because, by good fortune, these are in alphabetical order, string
+   collating can be used to compare version strings.  Be aware that
+   the 'e' designation will (naturally) be unstable and might be
+   incompatible with itself.  For gcc 3.4 experimental, it would be
+   '304e' (0x33303465).  When the major version reaches 10, the
+   letters A-Z will be used.  Assuming minor increments releases every
+   6 months, we have to make a major increment every 50 years.
+   Assuming major increments releases every 5 years, we're ok for the
+   next 155 years -- good enough for me.
+
+   A record has a tag, length and variable amount of data.
+
+   	record: header data
+	header: int32:tag int32:length
+	data: item*
+
+   Records are not nested, but there is a record hierarchy.  Tag
+   numbers reflect this hierarchy.  Tags are unique across note and
+   data files.  Some record types have a varying amount of data.  The
+   LENGTH is the number of 4bytes that follow and is usually used to
+   determine how much data.  The tag value is split into 4 8-bit
+   fields, one for each of four possible levels.  The most significant
+   is allocated first.  Unused levels are zero.  Active levels are
+   odd-valued, so that the LSB of the level is one.  A sub-level
+   incorporates the values of its superlevels.  This formatting allows
+   you to determine the tag hierarchy, without understanding the tags
+   themselves, and is similar to the standard section numbering used
+   in technical documents.  Level values [1..3f] are used for common
+   tags, values [41..9f] for the notes file and [a1..ff] for the data
+   file.
+
+   The basic block graph file contains the following records
+   	note: unit function-graph*
+	unit: header int32:checksum string:source
+	function-graph: announce_function basic_blocks {arcs | lines}*
+	announce_function: header int32:ident int32:checksum
+		string:name string:source int32:lineno
+	basic_block: header int32:flags*
+	arcs: header int32:block_no arc*
+	arc:  int32:dest_block int32:flags
+        lines: header int32:block_no line*
+               int32:0 string:NULL
+	line:  int32:line_no | int32:0 string:filename
+
+   The BASIC_BLOCK record holds per-bb flags.  The number of blocks
+   can be inferred from its data length.  There is one ARCS record per
+   basic block.  The number of arcs from a bb is implicit from the
+   data length.  It enumerates the destination bb and per-arc flags.
+   There is one LINES record per basic block, it enumerates the source
+   lines which belong to that basic block.  Source file names are
+   introduced by a line number of 0, following lines are from the new
+   source file.  The initial source file for the function is NULL, but
+   the current source file should be remembered from one LINES record
+   to the next.  The end of a block is indicated by an empty filename
+   - this does not reset the current source file.  Note there is no
+   ordering of the ARCS and LINES records: they may be in any order,
+   interleaved in any manner.  The current filename follows the order
+   the LINES records are stored in the file, *not* the ordering of the
+   blocks they are for.
+
+   The data file contains the following records.
+        data: {unit function-data* summary:object summary:program*}*
+	unit: header int32:checksum
+        function-data:	announce_function arc_counts
+	announce_function: header int32:ident int32:checksum
+	arc_counts: header int64:count*
+	summary: int32:checksum {count-summary}GCOV_COUNTERS
+	count-summary:	int32:num int32:runs int64:sum
+			int64:max int64:sum_max
+
+   The ANNOUNCE_FUNCTION record is the same as that in the note file,
+   but without the source location.  The ARC_COUNTS gives the counter
+   values for those arcs that are instrumented.  The SUMMARY records
+   give information about the whole object file and about the whole
+   program.  The checksum is used for whole program summaries, and
+   disambiguates different programs which include the same
+   instrumented object file.  There may be several program summaries,
+   each with a unique checksum.  The object summary's checksum is zero.
+   Note that the data file might contain information from several runs
+   concatenated, or the data might be merged.
+
+   This file is included by both the compiler, gcov tools and the
+   runtime support library libgcov. IN_LIBGCOV and IN_GCOV are used to
+   distinguish which case is which.  If IN_LIBGCOV is nonzero,
+   libgcov is being built. If IN_GCOV is nonzero, the gcov tools are
+   being built. Otherwise the compiler is being built. IN_GCOV may be
+   positive or negative. If positive, we are compiling a tool that
+   requires additional functions (see the code for knowledge of what
+   those functions are).  */
+
+#ifndef GCC_GCOV_IO_H
+#define GCC_GCOV_IO_H
+
+#if IN_LIBGCOV
+/* About the target */
+
+#if BITS_PER_UNIT == 8
+typedef unsigned gcov_unsigned_t __attribute__ ((mode (SI)));
+typedef unsigned gcov_position_t __attribute__ ((mode (SI)));
+#if LONG_LONG_TYPE_SIZE > 32
+typedef signed gcov_type __attribute__ ((mode (DI)));
+#else
+typedef signed gcov_type __attribute__ ((mode (SI)));
+#endif
+#else
+#if BITS_PER_UNIT == 16
+typedef unsigned gcov_unsigned_t __attribute__ ((mode (HI)));
+typedef unsigned gcov_position_t __attribute__ ((mode (HI)));
+#if LONG_LONG_TYPE_SIZE > 32
+typedef signed gcov_type __attribute__ ((mode (SI)));
+#else
+typedef signed gcov_type __attribute__ ((mode (HI)));
+#endif
+#else
+typedef unsigned gcov_unsigned_t __attribute__ ((mode (QI)));
+typedef unsigned gcov_position_t __attribute__ ((mode (QI)));
+#if LONG_LONG_TYPE_SIZE > 32
+typedef signed gcov_type __attribute__ ((mode (HI)));
+#else
+typedef signed gcov_type __attribute__ ((mode (QI)));
+#endif
+#endif
+#endif
+
+
+#if defined (TARGET_POSIX_IO)
+#define GCOV_LOCKED 1
+#else
+#define GCOV_LOCKED 0
+#endif
+
+#else /* !IN_LIBGCOV */
+/* About the host */
+
+typedef unsigned gcov_unsigned_t;
+typedef unsigned gcov_position_t;
+/* gcov_type is typedef'd elsewhere for the compiler */
+#if IN_GCOV
+#define GCOV_LINKAGE static
+typedef HOST_WIDEST_INT gcov_type;
+#if IN_GCOV > 0
+#include <sys/types.h>
+#endif
+#else /*!IN_GCOV */
+#define GCOV_TYPE_SIZE (LONG_LONG_TYPE_SIZE > 32 ? 64 : 32)
+#endif
+
+#if defined (HOST_HAS_F_SETLKW)
+#define GCOV_LOCKED 1
+#else
+#define GCOV_LOCKED 0
+#endif
+
+#endif /* !IN_LIBGCOV */
+
+/* In gcov we want function linkage to be static.  In the compiler we want
+   it extern, so that they can be accessed from elsewhere.  In libgcov we
+   need these functions to be extern, so prefix them with __gcov.  In
+   libgcov they must also be hidden so that the instance in the executable
+   is not also used in a DSO.  */
+#if IN_LIBGCOV
+
+#include "tconfig.h"
+
+#define gcov_var __gcov_var
+#define gcov_open __gcov_open
+#define gcov_close __gcov_close
+#define gcov_write_tag_length __gcov_write_tag_length
+#define gcov_position __gcov_position
+#define gcov_seek __gcov_seek
+#define gcov_rewrite __gcov_rewrite
+#define gcov_is_error __gcov_is_error
+#define gcov_write_unsigned __gcov_write_unsigned
+#define gcov_write_counter __gcov_write_counter
+#define gcov_write_summary __gcov_write_summary
+#define gcov_read_unsigned __gcov_read_unsigned
+#define gcov_read_counter __gcov_read_counter
+#define gcov_read_summary __gcov_read_summary
+
+/* Poison these, so they don't accidentally slip in.  */
+#pragma GCC poison gcov_write_string gcov_write_tag gcov_write_length
+#pragma GCC poison gcov_read_string gcov_sync gcov_time gcov_magic
+
+#ifdef HAVE_GAS_HIDDEN
+#define ATTRIBUTE_HIDDEN  __attribute__ ((__visibility__ ("hidden")))
+#else
+#define ATTRIBUTE_HIDDEN
+#endif
+
+#else
+
+#define ATTRIBUTE_HIDDEN
+
+#endif
+
+#ifndef GCOV_LINKAGE
+#define GCOV_LINKAGE extern
+#endif
+
+/* File suffixes.  */
+#define GCOV_DATA_SUFFIX ".gcda"
+#define GCOV_NOTE_SUFFIX ".gcno"
+
+/* File magic. Must not be palindromes.  */
+#define GCOV_DATA_MAGIC ((gcov_unsigned_t)0x67636461) /* "gcda" */
+#define GCOV_NOTE_MAGIC ((gcov_unsigned_t)0x67636e6f) /* "gcno" */
+
+/* gcov-iov.h is automatically generated by the makefile from
+   version.c, it looks like
+   	#define GCOV_VERSION ((gcov_unsigned_t)0x89abcdef)
+*/
+#include "gcov-iov.h"
+
+/* Convert a magic or version number to a 4 character string.  */
+#define GCOV_UNSIGNED2STRING(ARRAY,VALUE)	\
+  ((ARRAY)[0] = (char)((VALUE) >> 24),		\
+   (ARRAY)[1] = (char)((VALUE) >> 16),		\
+   (ARRAY)[2] = (char)((VALUE) >> 8),		\
+   (ARRAY)[3] = (char)((VALUE) >> 0))
+
+/* The record tags.  Values [1..3f] are for tags which may be in either
+   file.  Values [41..9f] for those in the note file and [a1..ff] for
+   the data file.  The tag value zero is used as an explicit end of
+   file marker -- it is not required to be present.  */
+
+#define GCOV_TAG_FUNCTION	 ((gcov_unsigned_t)0x01000000)
+#define GCOV_TAG_FUNCTION_LENGTH (2)
+#define GCOV_TAG_BLOCKS		 ((gcov_unsigned_t)0x01410000)
+#define GCOV_TAG_BLOCKS_LENGTH(NUM) (NUM)
+#define GCOV_TAG_BLOCKS_NUM(LENGTH) (LENGTH)
+#define GCOV_TAG_ARCS		 ((gcov_unsigned_t)0x01430000)
+#define GCOV_TAG_ARCS_LENGTH(NUM)  (1 + (NUM) * 2)
+#define GCOV_TAG_ARCS_NUM(LENGTH)  (((LENGTH) - 1) / 2)
+#define GCOV_TAG_LINES		 ((gcov_unsigned_t)0x01450000)
+#define GCOV_TAG_COUNTER_BASE 	 ((gcov_unsigned_t)0x01a10000)
+#define GCOV_TAG_COUNTER_LENGTH(NUM) ((NUM) * 2)
+#define GCOV_TAG_COUNTER_NUM(LENGTH) ((LENGTH) / 2)
+#define GCOV_TAG_OBJECT_SUMMARY  ((gcov_unsigned_t)0xa1000000)
+#define GCOV_TAG_PROGRAM_SUMMARY ((gcov_unsigned_t)0xa3000000)
+#define GCOV_TAG_SUMMARY_LENGTH  \
+	(1 + GCOV_COUNTERS_SUMMABLE * (2 + 3 * 2))
+
+/* Counters that are collected.  */
+#define GCOV_COUNTER_ARCS 	0  /* Arc transitions.  */
+#define GCOV_COUNTERS_SUMMABLE	1  /* Counters which can be
+				      summaried.  */
+#define GCOV_FIRST_VALUE_COUNTER 1 /* The first of counters used for value
+				      profiling.  They must form a consecutive
+				      interval and their order must match
+				      the order of HIST_TYPEs in
+				      value-prof.h.  */
+#define GCOV_COUNTER_V_INTERVAL	1  /* Histogram of value inside an interval.  */
+#define GCOV_COUNTER_V_POW2	2  /* Histogram of exact power2 logarithm
+				      of a value.  */
+#define GCOV_COUNTER_V_SINGLE	3  /* The most common value of expression.  */
+#define GCOV_COUNTER_V_DELTA	4  /* The most common difference between
+				      consecutive values of expression.  */
+
+#define GCOV_COUNTER_V_INDIR	5  /* The most common indirect address */
+#define GCOV_COUNTER_AVERAGE	6  /* Compute average value passed to the
+				      counter.  */
+#define GCOV_COUNTER_IOR	7  /* IOR of the all values passed to
+				      counter.  */
+#define GCOV_LAST_VALUE_COUNTER 7  /* The last of counters used for value
+				      profiling.  */
+#define GCOV_COUNTERS		8
+
+/* Number of counters used for value profiling.  */
+#define GCOV_N_VALUE_COUNTERS \
+  (GCOV_LAST_VALUE_COUNTER - GCOV_FIRST_VALUE_COUNTER + 1)
+  
+  /* A list of human readable names of the counters */
+#define GCOV_COUNTER_NAMES	{"arcs", "interval", "pow2", "single", \
+				 "delta","indirect_call", "average", "ior"}
+  
+  /* Names of merge functions for counters.  */
+#define GCOV_MERGE_FUNCTIONS	{"__gcov_merge_add",	\
+				 "__gcov_merge_add",	\
+				 "__gcov_merge_add",	\
+				 "__gcov_merge_single",	\
+				 "__gcov_merge_delta",  \
+				 "__gcov_merge_single", \
+				 "__gcov_merge_add",	\
+				 "__gcov_merge_ior"}
+  
+/* Convert a counter index to a tag.  */
+#define GCOV_TAG_FOR_COUNTER(COUNT)				\
+	(GCOV_TAG_COUNTER_BASE + ((gcov_unsigned_t)(COUNT) << 17))
+/* Convert a tag to a counter.  */
+#define GCOV_COUNTER_FOR_TAG(TAG)					\
+	((unsigned)(((TAG) - GCOV_TAG_COUNTER_BASE) >> 17))
+/* Check whether a tag is a counter tag.  */
+#define GCOV_TAG_IS_COUNTER(TAG)				\
+	(!((TAG) & 0xFFFF) && GCOV_COUNTER_FOR_TAG (TAG) < GCOV_COUNTERS)
+
+/* The tag level mask has 1's in the position of the inner levels, &
+   the lsb of the current level, and zero on the current and outer
+   levels.  */
+#define GCOV_TAG_MASK(TAG) (((TAG) - 1) ^ (TAG))
+
+/* Return nonzero if SUB is an immediate subtag of TAG.  */
+#define GCOV_TAG_IS_SUBTAG(TAG,SUB)				\
+	(GCOV_TAG_MASK (TAG) >> 8 == GCOV_TAG_MASK (SUB) 	\
+	 && !(((SUB) ^ (TAG)) & ~GCOV_TAG_MASK(TAG)))
+
+/* Return nonzero if SUB is at a sublevel to TAG.  */
+#define GCOV_TAG_IS_SUBLEVEL(TAG,SUB)				\
+     	(GCOV_TAG_MASK (TAG) > GCOV_TAG_MASK (SUB))
+
+/* Basic block flags.  */
+#define GCOV_BLOCK_UNEXPECTED	(1 << 1)
+
+/* Arc flags.  */
+#define GCOV_ARC_ON_TREE 	(1 << 0)
+#define GCOV_ARC_FAKE		(1 << 1)
+#define GCOV_ARC_FALLTHROUGH	(1 << 2)
+
+/* Structured records.  */
+
+/* Cumulative counter data.  */
+struct gcov_ctr_summary
+{
+  gcov_unsigned_t num;		/* number of counters.  */
+  gcov_unsigned_t runs;		/* number of program runs */
+  gcov_type sum_all;		/* sum of all counters accumulated.  */
+  gcov_type run_max;		/* maximum value on a single run.  */
+  gcov_type sum_max;    	/* sum of individual run max values.  */
+};
+
+/* Object & program summary record.  */
+struct gcov_summary
+{
+  gcov_unsigned_t checksum;	/* checksum of program */
+  struct gcov_ctr_summary ctrs[GCOV_COUNTERS_SUMMABLE];
+};
+
+/* Structures embedded in coveraged program.  The structures generated
+   by write_profile must match these.  */
+
+#if IN_LIBGCOV
+/* Information about a single function.  This uses the trailing array
+   idiom. The number of counters is determined from the counter_mask
+   in gcov_info.  We hold an array of function info, so have to
+   explicitly calculate the correct array stride.  */
+struct gcov_fn_info
+{
+  gcov_unsigned_t ident;	/* unique ident of function */
+  gcov_unsigned_t checksum;	/* function checksum */
+  unsigned n_ctrs[0];		/* instrumented counters */
+};
+
+/* Type of function used to merge counters.  */
+typedef void (*gcov_merge_fn) (gcov_type *, gcov_unsigned_t);
+
+/* Information about counters.  */
+struct gcov_ctr_info
+{
+  gcov_unsigned_t num;		/* number of counters.  */
+  gcov_type *values;		/* their values.  */
+  gcov_merge_fn merge;  	/* The function used to merge them.  */
+};
+
+/* Information about a single object file.  */
+struct gcov_info
+{
+  gcov_unsigned_t version;	/* expected version number */
+  struct gcov_info *next;	/* link to next, used by libgcov */
+
+  gcov_unsigned_t stamp;	/* uniquifying time stamp */
+  const char *filename;		/* output file name */
+  
+  unsigned n_functions;		/* number of functions */
+  const struct gcov_fn_info *functions; /* table of functions */
+
+  unsigned ctr_mask;		/* mask of counters instrumented.  */
+  struct gcov_ctr_info counts[0]; /* count data. The number of bits
+				     set in the ctr_mask field
+				     determines how big this array
+				     is.  */
+};
+
+/* Register a new object file module.  */
+extern void __gcov_init (struct gcov_info *) ATTRIBUTE_HIDDEN;
+
+/* Called before fork, to avoid double counting.  */
+extern void __gcov_flush (void) ATTRIBUTE_HIDDEN;
+
+/* The merge function that just sums the counters.  */
+extern void __gcov_merge_add (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+
+/* The merge function to choose the most common value.  */
+extern void __gcov_merge_single (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+
+/* The merge function to choose the most common difference between
+   consecutive values.  */
+extern void __gcov_merge_delta (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+
+/* The merge function that just ors the counters together.  */
+extern void __gcov_merge_ior (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+
+/* The profiler functions.  */
+extern void __gcov_interval_profiler (gcov_type *, gcov_type, int, unsigned); 
+extern void __gcov_pow2_profiler (gcov_type *, gcov_type);
+extern void __gcov_one_value_profiler (gcov_type *, gcov_type);
+extern void __gcov_indirect_call_profiler (gcov_type *, gcov_type, void *, void *);
+extern void __gcov_average_profiler (gcov_type *, gcov_type);
+extern void __gcov_ior_profiler (gcov_type *, gcov_type);
+
+#ifndef inhibit_libc
+/* The wrappers around some library functions..  */
+extern pid_t __gcov_fork (void) ATTRIBUTE_HIDDEN;
+extern int __gcov_execl (const char *, char *, ...) ATTRIBUTE_HIDDEN;
+extern int __gcov_execlp (const char *, char *, ...) ATTRIBUTE_HIDDEN;
+extern int __gcov_execle (const char *, char *, ...) ATTRIBUTE_HIDDEN;
+extern int __gcov_execv (const char *, char *const []) ATTRIBUTE_HIDDEN;
+extern int __gcov_execvp (const char *, char *const []) ATTRIBUTE_HIDDEN;
+extern int __gcov_execve (const char *, char  *const [], char *const [])
+  ATTRIBUTE_HIDDEN;
+#endif
+
+#endif /* IN_LIBGCOV */
+
+#if IN_LIBGCOV >= 0
+
+/* Optimum number of gcov_unsigned_t's read from or written to disk.  */
+#define GCOV_BLOCK_SIZE (1 << 10)
+
+GCOV_LINKAGE struct gcov_var
+{
+  FILE *file;
+  gcov_position_t start;	/* Position of first byte of block */
+  unsigned offset;		/* Read/write position within the block.  */
+  unsigned length;		/* Read limit in the block.  */
+  unsigned overread;		/* Number of words overread.  */
+  int error;			/* < 0 overflow, > 0 disk error.  */
+  int mode;	                /* < 0 writing, > 0 reading */
+#if IN_LIBGCOV
+  /* Holds one block plus 4 bytes, thus all coverage reads & writes
+     fit within this buffer and we always can transfer GCOV_BLOCK_SIZE
+     to and from the disk. libgcov never backtracks and only writes 4
+     or 8 byte objects.  */
+  gcov_unsigned_t buffer[GCOV_BLOCK_SIZE + 1];
+#else
+  int endian;			/* Swap endianness.  */
+  /* Holds a variable length block, as the compiler can write
+     strings and needs to backtrack.  */
+  size_t alloc;
+  gcov_unsigned_t *buffer;
+#endif
+} gcov_var ATTRIBUTE_HIDDEN;
+
+/* Functions for reading and writing gcov files. In libgcov you can
+   open the file for reading then writing. Elsewhere you can open the
+   file either for reading or for writing. When reading a file you may
+   use the gcov_read_* functions, gcov_sync, gcov_position, &
+   gcov_error. When writing a file you may use the gcov_write
+   functions, gcov_seek & gcov_error. When a file is to be rewritten
+   you use the functions for reading, then gcov_rewrite then the
+   functions for writing.  Your file may become corrupted if you break
+   these invariants.  */
+#if IN_LIBGCOV
+GCOV_LINKAGE int gcov_open (const char */*name*/) ATTRIBUTE_HIDDEN;
+#else
+GCOV_LINKAGE int gcov_open (const char */*name*/, int /*direction*/);
+GCOV_LINKAGE int gcov_magic (gcov_unsigned_t, gcov_unsigned_t);
+#endif
+GCOV_LINKAGE int gcov_close (void) ATTRIBUTE_HIDDEN;
+
+/* Available everywhere.  */
+static gcov_position_t gcov_position (void);
+static int gcov_is_error (void);
+
+GCOV_LINKAGE gcov_unsigned_t gcov_read_unsigned (void) ATTRIBUTE_HIDDEN;
+GCOV_LINKAGE gcov_type gcov_read_counter (void) ATTRIBUTE_HIDDEN;
+GCOV_LINKAGE void gcov_read_summary (struct gcov_summary *) ATTRIBUTE_HIDDEN;
+
+#if IN_LIBGCOV
+/* Available only in libgcov */
+GCOV_LINKAGE void gcov_write_counter (gcov_type) ATTRIBUTE_HIDDEN;
+GCOV_LINKAGE void gcov_write_tag_length (gcov_unsigned_t, gcov_unsigned_t)
+    ATTRIBUTE_HIDDEN;
+GCOV_LINKAGE void gcov_write_summary (gcov_unsigned_t /*tag*/,
+				      const struct gcov_summary *)
+    ATTRIBUTE_HIDDEN;
+static void gcov_rewrite (void);
+GCOV_LINKAGE void gcov_seek (gcov_position_t /*position*/) ATTRIBUTE_HIDDEN;
+#else
+/* Available outside libgcov */
+GCOV_LINKAGE const char *gcov_read_string (void);
+GCOV_LINKAGE void gcov_sync (gcov_position_t /*base*/,
+			     gcov_unsigned_t /*length */);
+#endif
+
+#if !IN_GCOV
+/* Available outside gcov */
+GCOV_LINKAGE void gcov_write_unsigned (gcov_unsigned_t) ATTRIBUTE_HIDDEN;
+#endif
+
+#if !IN_GCOV && !IN_LIBGCOV
+/* Available only in compiler */
+GCOV_LINKAGE void gcov_write_string (const char *);
+GCOV_LINKAGE gcov_position_t gcov_write_tag (gcov_unsigned_t);
+GCOV_LINKAGE void gcov_write_length (gcov_position_t /*position*/);
+#endif
+
+#if IN_GCOV > 0
+/* Available in gcov */
+GCOV_LINKAGE time_t gcov_time (void);
+#endif
+
+/* Save the current position in the gcov file.  */
+
+static inline gcov_position_t
+gcov_position (void)
+{
+  gcc_assert (gcov_var.mode > 0);
+  return gcov_var.start + gcov_var.offset;
+}
+
+/* Return nonzero if the error flag is set.  */
+
+static inline int
+gcov_is_error (void)
+{
+  return gcov_var.file ? gcov_var.error : 1;
+}
+
+#if IN_LIBGCOV
+/* Move to beginning of file and initialize for writing.  */
+
+static inline void
+gcov_rewrite (void)
+{
+  gcc_assert (gcov_var.mode > 0);
+  gcov_var.mode = -1;
+  gcov_var.start = 0;
+  gcov_var.offset = 0;
+  fseek (gcov_var.file, 0L, SEEK_SET);
+}
+#endif
+
+#endif /* IN_LIBGCOV >= 0 */
+
+#endif /* GCC_GCOV_IO_H */