[clang] [Clang] Add additional tests for constexpr initialization (PR #181965)
Samrudh Nelli via cfe-commits
cfe-commits at lists.llvm.org
Sat Mar 7 03:40:47 PST 2026
https://github.com/SamrudhNelli updated https://github.com/llvm/llvm-project/pull/181965
>From 9e8bcf6b421e0f285be990f0e667bf579949e618 Mon Sep 17 00:00:00 2001
From: Samrudh Nelli <samrudhnelli at gmail.com>
Date: Wed, 18 Feb 2026 11:42:51 +0530
Subject: [PATCH 1/2] [Clang] Add additional tests for constexpr initialization
---
clang/test/AST/ByteCode/constexpr.c | 6 ++++++
clang/test/Sema/constexpr.c | 6 ++++++
2 files changed, 12 insertions(+)
diff --git a/clang/test/AST/ByteCode/constexpr.c b/clang/test/AST/ByteCode/constexpr.c
index dfe3d667f27cc..b345d5e67aa43 100644
--- a/clang/test/AST/ByteCode/constexpr.c
+++ b/clang/test/AST/ByteCode/constexpr.c
@@ -313,6 +313,12 @@ constexpr int *V84 = 42;
constexpr int *V85 = nullptr;
constexpr int *V91 = 0.;
// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
+constexpr int *V92 = 0.0f;
+// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'float'}}
+constexpr int *V93 = 0e0;
+// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
+constexpr int *V94 = 0x0p0;
+// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
// Check that constexpr variables should not be VLAs.
void f6(const int P1) {
diff --git a/clang/test/Sema/constexpr.c b/clang/test/Sema/constexpr.c
index 04da0f56a741d..3a6b49fd90748 100644
--- a/clang/test/Sema/constexpr.c
+++ b/clang/test/Sema/constexpr.c
@@ -313,6 +313,12 @@ constexpr int *V84 = 42;
constexpr int *V85 = nullptr;
constexpr int *V91 = 0.0;
// expected-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
+constexpr int *V92 = 0.0f;
+// expected-error at -1 {{initializing 'int *const' with an expression of incompatible type 'float'}}
+constexpr int *V93 = 0e0;
+// expected-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
+constexpr int *V94 = 0x0p0;
+// expected-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
// Check that constexpr variables should not be VLAs.
void f6(const int P1) {
>From bdc87d947b981a1ff4ebcb0fa4b3277c7b04f289 Mon Sep 17 00:00:00 2001
From: Samrudh Nelli <samrudhnelli at gmail.com>
Date: Sat, 7 Mar 2026 17:08:07 +0530
Subject: [PATCH 2/2] Remove duplicate test AST/ByteCode/constexpr.c in favour
of Sema/constexpr.c
---
clang/test/AST/ByteCode/constexpr.c | 376 ----------------------------
1 file changed, 376 deletions(-)
delete mode 100644 clang/test/AST/ByteCode/constexpr.c
diff --git a/clang/test/AST/ByteCode/constexpr.c b/clang/test/AST/ByteCode/constexpr.c
deleted file mode 100644
index b345d5e67aa43..0000000000000
--- a/clang/test/AST/ByteCode/constexpr.c
+++ /dev/null
@@ -1,376 +0,0 @@
-// RUN: %clang_cc1 -std=c23 -verify=ref,both -triple x86_64 -pedantic -Wno-conversion -Wno-constant-conversion -Wno-div-by-zero %s
-// RUN: %clang_cc1 -std=c23 -verify=expected,both -triple x86_64 -pedantic -Wno-conversion -Wno-constant-conversion -Wno-div-by-zero -fexperimental-new-constant-interpreter %s
-
-// Check that constexpr only applies to variables.
-constexpr void f0() {} // both-error {{'constexpr' can only be used in variable declarations}}
-constexpr const int f1() { return 0; } // both-error {{'constexpr' can only be used in variable declarations}}
-
-constexpr struct S1 { int f; }; //both-error {{struct cannot be marked constexpr}}
-constexpr struct S2 ; // both-error {{struct cannot be marked constexpr}}
-constexpr union U1; // both-error {{union cannot be marked constexpr}}
-constexpr union U2 {int a; float b;}; // both-error {{union cannot be marked constexpr}}
-constexpr enum E1 {A = 1, B = 2} ; // both-error {{enum cannot be marked constexpr}}
-struct S3 {
- static constexpr int f = 0; // both-error {{type name does not allow storage class}}
- // both-error at -1 {{type name does not allow constexpr}}
- // both-error at -2 {{expected ';' at end}}
- constexpr int f1 = 0;
- // both-error at -1 {{type name does not allow constexpr}}
- // both-error at -2 {{expected ';' at end}}
-};
-
-constexpr; // both-error {{'constexpr' can only be used in variable declarations}}
-constexpr int V1 = 3;
-constexpr float V2 = 7.0;
-int V3 = (constexpr)3; // both-error {{expected expression}}
-
-void f2() {
- constexpr int a = 0;
- constexpr float b = 1.7f;
-}
-
-// Check how constexpr works with other storage-class specifiers.
-constexpr auto V4 = 1;
-constexpr static auto V5 = 1;
-constexpr static const auto V6 = 1;
-constexpr static const int V7 = 1;
-constexpr static int V8 = 1;
-constexpr auto Ulong = 1L;
-constexpr auto CompoundLiteral = (int){13};
-constexpr auto DoubleCast = (double)(1 / 3);
-constexpr auto String = "this is a string"; // both-error {{constexpr pointer initializer is not null}}
-constexpr signed auto Long = 1L; // both-error {{'auto' cannot be signed or unsigned}}
-_Static_assert(_Generic(Ulong, long : 1));
-_Static_assert(_Generic(CompoundLiteral, int : 1));
-_Static_assert(_Generic(DoubleCast, double : 1));
-_Static_assert(_Generic(String, char* : 1));
-
-typedef constexpr int Foo; // both-error {{typedef cannot be constexpr}}
-constexpr typedef int Bar; // both-error {{typedef cannot be constexpr}}
-
-void f3(constexpr register int P1) { // both-error {{function parameter cannot be constexpr}}
- constexpr register int V9 = 0;
- constexpr register auto V10 = 0.0;
-}
-
-constexpr thread_local int V11 = 38; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
-constexpr static thread_local double V12 = 38; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
-constexpr extern thread_local char V13; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
-// both-error at -1 {{cannot combine with previous 'extern' declaration specifier}}
-// both-error at -2 {{constexpr variable declaration must be a definition}}
-constexpr thread_local short V14 = 38; // both-error {{cannot combine with previous '_Thread_local' declaration specifier}}
-
-// Check how constexpr works with qualifiers.
-constexpr _Atomic int V15 = 0; // both-error {{constexpr variable cannot have type 'const _Atomic(int)'}}
-constexpr _Atomic(int) V16 = 0; // both-error {{constexpr variable cannot have type 'const _Atomic(int)'}}
-
-constexpr volatile int V17 = 0; // both-error {{constexpr variable cannot have type 'const volatile int'}}
-
-constexpr int * restrict V18 = 0; // both-error {{constexpr variable cannot have type 'int *const restrict'}}
-
-constexpr extern char Oops = 1; // both-error {{cannot combine with previous 'extern' declaration specifier}} \
- // both-warning {{'extern' variable has an initializer}}
-
-constexpr int * restrict * Oops1 = 0;
-
-typedef _Atomic(int) TheA;
-typedef volatile short TheV;
-typedef float * restrict TheR;
-
-constexpr TheA V19[3] = {};
-// both-error at -1 {{constexpr variable cannot have type 'const TheA[3]' (aka 'const _Atomic(int)[3]')}}
-constexpr TheV V20[3] = {};
-// both-error at -1 {{constexpr variable cannot have type 'const TheV[3]' (aka 'const volatile short[3]')}}
-constexpr TheR V21[3] = {};
-// both-error at -1 {{constexpr variable cannot have type 'const TheR[3]' (aka 'float *restrict const[3]')}}
-
-struct HasA {
- TheA f;
- int b;
-};
-
-struct HasV {
- float b;
- TheV f;
-};
-
-struct HasR {
- short b;
- int a;
- TheR f;
-};
-
-constexpr struct HasA V22[2] = {};
-// both-error at -1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
-constexpr struct HasV V23[2] = {};
-// both-error at -1 {{constexpr variable cannot have type 'TheV' (aka 'volatile short')}}
-constexpr struct HasR V24[2] = {};
-// both-error at -1 {{constexpr variable cannot have type 'TheR' (aka 'float *restrict')}}
-
-union U3 {
- float a;
- union {
- struct HasA f;
- struct HasR f1;
- };
-};
-
-constexpr union U3 V25 = {};
-// both-error at -1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
-constexpr union U3 V26[8] = {};
-// both-error at -1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
-
-struct S4 {
- union U3 f[3];
-};
-
-constexpr struct S4 V27 = {};
-// both-error at -1 {{constexpr variable cannot have type 'TheA' (aka '_Atomic(int)')}}
-constexpr const int V28 = 28;
-
-struct S {
- union {
- volatile int i;
- };
- int j;
-};
-
-constexpr struct S s = {}; // both-error {{constexpr variable cannot have type 'volatile int'}}
-
-// Check that constexpr variable must have a valid initializer which is a
-// constant expression.
-constexpr int V29;
-// both-error at -1 {{constexpr variable 'V29' must be initialized by a constant expression}}
-
-struct S5 {
- int f;
-};
-
-constexpr struct S5 V30;
-// both-error at -1 {{constexpr variable 'V30' must be initialized by a constant expression}}
-constexpr struct S5 V31 = {};
-
-int randomFoo() { return 7; }
-
-constexpr float V32 = randomFoo();
-// both-error at -1 {{constexpr variable 'V32' must be initialized by a constant expression}}
-
-const int V33 = 4;
-const int V34 = 0;
-const int V35 = 2;
-
-constexpr int V36 = V33 / V34;
-// both-error at -1 {{constexpr variable 'V36' must be initialized by a constant expression}}
-constexpr int V37 = V33 / V35;
-// both-error at -1 {{constexpr variable 'V37' must be initialized by a constant expression}}
-constexpr int V38 = 3;
-constexpr int V39 = V38 / V38;
-constexpr int V40 = V38 / 2;
-constexpr int V41 = V38 / 0;
-// both-error at -1 {{constexpr variable 'V41' must be initialized by a constant expression}}
-// both-note at -2 {{division by zero}}
-constexpr int V42 = V38 & 0;
-
-constexpr struct S5 V43 = { randomFoo() };
-// both-error at -1 {{constexpr variable 'V43' must be initialized by a constant expression}}
-constexpr struct S5 V44 = { 0 };
-constexpr struct S5 V45 = { V38 / 0 };
-// both-error at -1 {{constexpr variable 'V45' must be initialized by a constant expression}}
-// both-note at -2 {{division by zero}}
-
-constexpr float V46[3] = {randomFoo() };
-// both-error at -1 {{constexpr variable 'V46' must be initialized by a constant expression}}
-constexpr struct S5 V47[3] = {randomFoo() };
-// both-error at -1 {{constexpr variable 'V47' must be initialized by a constant expression}}
-
-const static int V48 = V38;
-constexpr static int V49 = V48;
-// both-error at -1 {{constexpr variable 'V49' must be initialized by a constant expression}}
-
-void f4(const int P1) {
- constexpr int V = P1;
-// both-error at -1 {{constexpr variable 'V' must be initialized by a constant expression}}
-
- constexpr int V1 = 12;
- constexpr const int *V2 = &V1;
-// both-error at -1 {{constexpr variable 'V2' must be initialized by a constant expression}}
-}
-
-// Check that initializer for constexpr variable should match the type of the
-// variable and is exactly representable int the variable's type.
-
-struct S6 {
- unsigned char a;
-};
-
-struct S7 {
- union {
- float a;
- };
- unsigned int b;
-};
-
-struct S8 {
- unsigned char a[3];
- unsigned int b[3];
-};
-
-constexpr struct S8 DesigInit = {.b = {299, 7, 8}, .a = {-1, 7, 8}};
-// both-error at -1 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'unsigned char'}}
-
-void f5() {
- constexpr char V50 = 300;
- // both-error at -1 {{constexpr initializer evaluates to 300 which is not exactly representable in type 'const char'}}
- constexpr float V51 = 1.0 / 3.0;
- // both-error at -1 {{constexpr initializer evaluates to 3.333333e-01 which is not exactly representable in type 'const float'}}
- constexpr float V52 = 0.7;
- // both-error at -1 {{constexpr initializer evaluates to 7.000000e-01 which is not exactly representable in type 'const float'}}
- constexpr float V53 = 1.0f / 3.0f;
- constexpr float V54 = 432000000000;
- // both-error at -1 {{constexpr initializer evaluates to 432000000000 which is not exactly representable in type 'const float'}}
- constexpr unsigned char V55[] = {
- "\xAF",
- // both-error at -1 {{constexpr initializer evaluates to -81 which is not exactly representable in type 'const unsigned char'}}
- };
-
- constexpr unsigned char V56[] = {
- u8"\xAF",
- };
- constexpr struct S6 V57 = {299};
- // both-error at -1 {{constexpr initializer evaluates to 299 which is not exactly representable in type 'unsigned char'}}
- constexpr struct S6 V58 = {-299};
- // both-error at -1 {{constexpr initializer evaluates to -299 which is not exactly representable in type 'unsigned char'}}
- constexpr double V59 = 0.5;
- constexpr double V60 = 1.0;
- constexpr float V61 = V59 / V60;
- constexpr double V62 = 1.7;
- constexpr float V63 = V59 / V62;
- // both-error at -1 {{constexpr initializer evaluates to 2.941176e-01 which is not exactly representable in type 'const float'}}
-
- constexpr unsigned char V64 = '\xAF';
- // both-error at -1 {{constexpr initializer evaluates to -81 which is not exactly representable in type 'const unsigned char'}}
- constexpr unsigned char V65 = u8'\xAF';
-
- constexpr char V66[3] = {300};
- // both-error at -1 {{constexpr initializer evaluates to 300 which is not exactly representable in type 'const char'}}
- constexpr struct S6 V67[3] = {300};
- // both-error at -1 {{constexpr initializer evaluates to 300 which is not exactly representable in type 'unsigned char'}}
-
- constexpr struct S7 V68 = {0.3, -1 };
- // both-error at -1 {{constexpr initializer evaluates to 3.000000e-01 which is not exactly representable in type 'float'}}
- // both-error at -2 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'unsigned int'}}
- constexpr struct S7 V69 = {0.5, -1 };
- // both-error at -1 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'unsigned int'}}
- constexpr struct S7 V70[3] = {{123456789}};
- // both-error at -1 {{constexpr initializer evaluates to 123456789 which is not exactly representable in type 'float'}}
-
- constexpr int V71 = 0.3;
- // both-error at -1 {{constexpr initializer for type 'const int' is of type 'double'}}
- constexpr int V72 = V59;
- // both-error at -1 {{constexpr initializer for type 'const int' is of type 'const double'}}
- constexpr struct S6 V73 = {V59};
- // both-error at -1 {{constexpr initializer for type 'unsigned char' is of type 'const double'}}
-
- constexpr float V74 = 1;
- constexpr float V75 = V59;
- constexpr unsigned int V76[3] = {0.5};
- // both-error at -1 {{constexpr initializer for type 'const unsigned int' is of type 'double'}}
-
- constexpr _Complex float V77 = 0;
- constexpr float V78 = V77;
- // both-error at -1 {{constexpr initializer for type 'const float' is of type 'const _Complex float'}}
- constexpr int V79 = V77;
- // both-error at -1 {{constexpr initializer for type 'const int' is of type 'const _Complex float'}}
-
-}
-
-constexpr char string[] = "test""ing this out\xFF";
-constexpr unsigned char ustring[] = "test""ing this out\xFF";
-// both-error at -1 {{constexpr initializer evaluates to -1 which is not exactly representable in type 'const unsigned char'}}
-constexpr char u8string[] = u8"test"u8"ing this out\xFF";
-// both-error at -1 {{constexpr initializer evaluates to 255 which is not exactly representable in type 'const char'}}
-constexpr unsigned char u8ustring[] = u8"test"u8"ing this out\xFF";
-constexpr unsigned short uustring[] = u"test"u"ing this out\xFF";
-constexpr unsigned int Ustring[] = U"test"U"ing this out\xFF";
-constexpr unsigned char Arr2[6][6] = {
- {"ek\xFF"}, {"ek\xFF"}
-// both-error at -1 2{{constexpr initializer evaluates to -1 which is not exactly representable in type 'const unsigned char'}}
-};
-
-constexpr int i = (12);
-constexpr int j = (i);
-constexpr unsigned jneg = (-i);
-// both-error at -1 {{constexpr initializer evaluates to -12 which is not exactly representable in type 'const unsigned int'}}
-
-// Check that initializer for pointer constexpr variable should be null.
-constexpr int V80 = 3;
-constexpr const int *V81 = &V80;
-// both-error at -1 {{constexpr pointer initializer is not null}}
-constexpr int *V82 = 0;
-constexpr int *V83 = V82;
-constexpr int *V84 = 42;
-// both-error at -1 {{constexpr pointer initializer is not null}}
-constexpr int *V85 = nullptr;
-constexpr int *V91 = 0.;
-// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
-constexpr int *V92 = 0.0f;
-// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'float'}}
-constexpr int *V93 = 0e0;
-// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
-constexpr int *V94 = 0x0p0;
-// both-error at -1 {{initializing 'int *const' with an expression of incompatible type 'double'}}
-
-// Check that constexpr variables should not be VLAs.
-void f6(const int P1) {
- constexpr int V86[P1] = {};
-// both-error at -1 {{constexpr variable cannot have type 'const int[P1]'}}
- const int V87 = 3;
- constexpr int V88[V87] = {};
-// both-warning at -1 {{variable length array folded to constant array as an extension}}
- int V89 = 7;
- constexpr int V90[V89] = {};
-// both-error at -1 {{constexpr variable cannot have type 'const int[V89]'}}
-}
-
-void f7(int n, int array[n]) {
- constexpr typeof(array) foo = 0; // Accepted because array is a pointer type, not a VLA type
- int (*(*fp)(int n))[n];
- constexpr typeof(fp) bar = 0; // both-error {{constexpr variable cannot have type 'const typeof (fp)' (aka 'int (*(*const)(int))[n]')}}
-}
-
-// Check how constexpr works with NaNs and infinities.
-#define FLT_NAN __builtin_nanf("1")
-#define DBL_NAN __builtin_nan("1")
-#define LD_NAN __builtin_nanf("1")
-#define FLT_SNAN __builtin_nansf("1")
-#define DBL_SNAN __builtin_nans("1")
-#define LD_SNAN __builtin_nansl("1")
-#define INF __builtin_inf()
-void infsNaNs() {
- // Inf and quiet NaN is always fine, signaling NaN must have the same type.
- constexpr float fl0 = INF;
- constexpr float fl1 = (long double)INF;
- constexpr float fl2 = (long double)FLT_NAN;
- constexpr float fl3 = FLT_NAN;
- constexpr float fl5 = DBL_NAN;
- constexpr float fl6 = LD_NAN;
- constexpr float fl7 = DBL_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const float'}}
- constexpr float fl8 = LD_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const float'}}
-
- constexpr double db0 = FLT_NAN;
- constexpr double db2 = DBL_NAN;
- constexpr double db3 = DBL_SNAN;
- constexpr double db4 = FLT_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const double'}}
- constexpr double db5 = LD_SNAN; // both-error {{constexpr initializer evaluates to nan which is not exactly representable in type 'const double'}}
- constexpr double db6 = INF;
-}
-
-constexpr struct S9 s9 = { }; // both-error {{variable has incomplete type 'const struct S9'}} \
- // both-note {{forward declaration of 'struct S9'}}
-
-struct S10 {
- signed long long i : 8;
-};
-constexpr struct S10 c = { 255 };
-// FIXME-expected-error at -1 {{constexpr initializer evaluates to 255 which is not exactly representable in 'long long' bit-field with width 8}}
-// See: GH#101299
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