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C library: Refine and improve stdio models
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Fixes portability to FreeBSD, which redefines several functions as
macros that would only conditionally call that function. Also, ensure
that stdin/stdout/stderr point to valid objects when those are
fdopen'ed.
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@tautschnig
tautschnig committed Dec 19, 2023
1 parent 3a1272a commit 76b3c4e
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Showing 4 changed files with 129 additions and 24 deletions.
3 changes: 3 additions & 0 deletions .github/workflows/bsd.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ jobs:
# gmake TAGS='[!shouldfail]' -C jbmc/unit test
echo "Run regression tests"
gmake -C regression/cbmc test
gmake -C regression/cbmc-library test
# gmake -C regression test-parallel JOBS=2
# gmake -C regression/cbmc test-paths-lifo
# env PATH=$PATH:`pwd`/src/solvers gmake -C regression/cbmc test-cprover-smt2
Expand Down Expand Up @@ -123,6 +124,7 @@ jobs:
# gmake TAGS='[!shouldfail]' -C jbmc/unit test
echo "Run regression tests"
gmake -C regression/cbmc test
gmake -C regression/cbmc-library test
# gmake -C regression test-parallel JOBS=2
# gmake -C regression/cbmc test-paths-lifo
# env PATH=$PATH:`pwd`/src/solvers gmake -C regression/cbmc test-cprover-smt2
Expand Down Expand Up @@ -187,6 +189,7 @@ jobs:
echo "Run regression tests"
# TODO: we need to model some more library functions
gmake -C regression/cbmc test || true
gmake -C regression/cbmc-library test || true
# gmake -C regression test-parallel JOBS=2
# gmake -C regression/cbmc test-paths-lifo
# env PATH=$PATH:`pwd`/src/solvers gmake -C regression/cbmc test-cprover-smt2
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8 changes: 2 additions & 6 deletions regression/cbmc-library/fileno-01/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,14 +3,10 @@

int main()
{
// requires initialization of stdin/stdout/stderr
// assert(fileno(stdin) == 0);
// assert(fileno(stdout) == 1);
// assert(fileno(stderr) == 2);

int fd;
FILE *some_file = fdopen(fd, "");
assert(fileno(some_file) >= -1);
if(some_file)
assert(fileno(some_file) >= -1);

return 0;
}
3 changes: 2 additions & 1 deletion regression/contracts-dfcc/variant_multidimensional_ackermann/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,8 @@ int main()
int n = 5;
int result = ackermann(m, n);

printf("Result of the Ackermann function: %d\n", result);
// we don't currently have contracts on what printf is assigning to
// printf("Result of the Ackermann function: %d\n", result);
return 0;
}

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139 changes: 122 additions & 17 deletions src/ansi-c/library/stdio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6,15 +6,7 @@
#define __CPROVER_STDIO_H_INCLUDED
#endif

/* undefine macros in OpenBSD's stdio.h that are problematic to the checker. */
#if defined(__OpenBSD__)
#undef getchar
#undef putchar
#undef getc
#undef feof
#undef ferror
#undef fileno
#endif

__CPROVER_bool __VERIFIER_nondet___CPROVER_bool(void);

Expand Down Expand Up @@ -197,7 +189,8 @@ __CPROVER_HIDE:;
__CPROVER_set_must(stream, "closed");
#endif
int return_value=__VERIFIER_nondet_int();
free(stream);
if(stream != stdin && stream != stdout && stream != stderr)
free(stream);
return return_value;
}

Expand All @@ -213,25 +206,83 @@ __CPROVER_HIDE:;
#define __CPROVER_STDLIB_H_INCLUDED
#endif

#ifndef __CPROVER_ERRNO_H_INCLUDED
# include <errno.h>
# define __CPROVER_ERRNO_H_INCLUDED
#endif

FILE *fdopen(int handle, const char *mode)
{
__CPROVER_HIDE:;
(void)handle;
if(handle < 0)
{
errno = EBADF;
return NULL;
}
(void)*mode;
#ifdef __CPROVER_STRING_ABSTRACTION
__CPROVER_assert(__CPROVER_is_zero_string(mode),
"fdopen zero-termination of 2nd argument");
#endif

#if !defined(__linux__) || defined(__GLIBC__)
FILE *f=malloc(sizeof(FILE));
#if defined(_WIN32) || defined(__OpenBSD__)
switch(handle)
{
case 0:
return stdin;
case 1:
return stdout;
case 2:
return stderr;
default:
{
FILE *f = malloc(sizeof(FILE));
__CPROVER_assume(fileno(f) == handle);
return f;
}
}
#else
// libraries need to expose the definition of FILE; this is the
# if !defined(__linux__) || defined(__GLIBC__)
static FILE stdin_file;
static FILE stdout_file;
static FILE stderr_file;
# else
// libraries need not expose the definition of FILE; this is the
// case for musl
FILE *f=malloc(sizeof(int));
#endif
static int stdin_file;
static int stdout_file;
static int stderr_file;
# endif

FILE *f = NULL;
switch(handle)
{
case 0:
stdin = &stdin_file;
__CPROVER_havoc_object(&stdin_file);
f = &stdin_file;
break;
case 1:
stdout = &stdout_file;
__CPROVER_havoc_object(&stdout_file);
f = &stdout_file;
break;
case 2:
stderr = &stderr_file;
__CPROVER_havoc_object(&stderr_file);
f = &stderr_file;
break;
default:
# if !defined(__linux__) || defined(__GLIBC__)
f = malloc(sizeof(FILE));
# else
f = malloc(sizeof(int));
# endif
}

__CPROVER_assume(fileno(f) == handle);
return f;
#endif
}

/* FUNCTION: _fdopen */
Expand All @@ -251,19 +302,60 @@ FILE *fdopen(int handle, const char *mode)
#define __CPROVER_STDLIB_H_INCLUDED
#endif

#ifndef __CPROVER_ERRNO_H_INCLUDED
# include <errno.h>
# define __CPROVER_ERRNO_H_INCLUDED
#endif

#ifdef __APPLE__

# ifndef LIBRARY_CHECK
FILE *stdin;
FILE *stdout;
FILE *stderr;
# endif

FILE *_fdopen(int handle, const char *mode)
{
__CPROVER_HIDE:;
(void)handle;
if(handle < 0)
{
errno = EBADF;
return NULL;
}
(void)*mode;
#ifdef __CPROVER_STRING_ABSTRACTION
__CPROVER_assert(__CPROVER_is_zero_string(mode),
"fdopen zero-termination of 2nd argument");
#endif

FILE *f=malloc(sizeof(FILE));
static FILE stdin_file;
static FILE stdout_file;
static FILE stderr_file;

FILE *f = NULL;
switch(handle)
{
case 0:
stdin = &stdin_file;
__CPROVER_havoc_object(&stdin_file);
f = &stdin_file;
break;
case 1:
stdout = &stdout_file;
__CPROVER_havoc_object(&stdout_file);
f = &stdout_file;
break;
case 2:
stderr = &stderr_file;
__CPROVER_havoc_object(&stderr_file);
f = &stderr_file;
break;
default:
f = malloc(sizeof(FILE));
}

__CPROVER_assume(fileno(f) == handle);
return f;
}
#endif
Expand Down Expand Up @@ -466,6 +558,8 @@ __CPROVER_HIDE:;
#define __CPROVER_STDIO_H_INCLUDED
#endif

#undef feof

int __VERIFIER_nondet_int(void);

int feof(FILE *stream)
Expand Down Expand Up @@ -498,6 +592,8 @@ int feof(FILE *stream)
#define __CPROVER_STDIO_H_INCLUDED
#endif

#undef ferror

int __VERIFIER_nondet_int(void);

int ferror(FILE *stream)
Expand Down Expand Up @@ -530,6 +626,8 @@ int ferror(FILE *stream)
#define __CPROVER_STDIO_H_INCLUDED
#endif

#undef fileno

int __VERIFIER_nondet_int(void);

int fileno(FILE *stream)
Expand Down Expand Up @@ -695,6 +793,8 @@ int fgetc(FILE *stream)
#define __CPROVER_STDIO_H_INCLUDED
#endif

#undef getc

int __VERIFIER_nondet_int(void);

int getc(FILE *stream)
Expand Down Expand Up @@ -731,6 +831,8 @@ int getc(FILE *stream)
#define __CPROVER_STDIO_H_INCLUDED
#endif

#undef getchar

int __VERIFIER_nondet_int(void);

int getchar(void)
Expand Down Expand Up @@ -1602,10 +1704,13 @@ FILE *__acrt_iob_func(unsigned fd)
switch(fd)
{
case 0:
__CPROVER_havoc_object(&stdin_file);
return &stdin_file;
case 1:
__CPROVER_havoc_object(&stdout_file);
return &stdout_file;
case 2:
__CPROVER_havoc_object(&stderr_file);
return &stderr_file;
default:
return (FILE *)0;
Expand Down

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